Critical Pollination Chemistry: Specific Sesquiterpene Floral Volatiles in Carrot Inhibit Honey Bee Feeding

Many plants rely on insect pollination, yet numerous agricultural plant-breeding programs focus on traits that appeal to growers and consumers instead of pollinators, leading to declining pollinator attraction and crop yields. Using hybrid carrot seed production as a model, we investigated low-yielding carrot varieties by analyzing sugars and minerals in nectar and floral volatile composition. While the analysis of nectar sugars and minerals did not reveal any key differences between the carrot varieties, differences between the 112 detected volatiles in 23 samples were observed. Numerous differentiating sesquiterpenes were identified in floral solvent extracts, and subsequent behavioral assays showed that β-ocimene from higher-yielding carrot varieties stimulated nectar feeding (attractant), while α- and β-selinene from lower-yielding lines decreased feeding (deterrents). Sesquiterpenes have previously been implicated in plant defense, suggesting a trade-off between pollination and protection. Our results highlight the importance of volatiles as regulators of pollinator attraction in agricultural settings.

Fly pollination drives convergence of flower coloration

Plant-pollinator interactions provide a natural experiment in signal evolution. Flowers are known to have evolved colour signals that maximise their ease of detection by the visual systems of important pollinators such as bees. Whilst most angiosperms are bee pollinated, our understanding on how the second largest group of pollinating insects, flies, may influence flower colour evolution is limited to the use of categorical models of colour discrimination that do not reflect the small colour differences commonly observed between and within flower species. Here we show by comparing flower signals that occur in different environments including total absence of bees, a mixture of bee and fly pollination within one plant family (Orchidaceae) from a single community, and typical flowers from a broad taxonomic sampling of the same geographic region, that perceptually different colours, empirically measured, do evolve in response to different types of insect pollinators. We show evidence of both convergence among fly-pollinated floral colours but also of divergence and displacement of colour signals in the absence of bee pollinators. Our findings give an insight into how both ecological and agricultural systems may be affected by changes in pollinator distributions around the world.

Climate change threatens New Guinea's biocultural heritage

New Guinea is the most biologically and linguistically diverse tropical island on Earth, yet the potential impacts of climate change on its biocultural heritage remain unknown. Analyzing 2353 endemic plant species distributions, we find that 63% of species are expected to have smaller geographic ranges by 2070. As a result, ecoregions may have an average of -70 ± 40 fewer species by 2070. Species with future geographic range contractions include 720 endemic plant species that are used by indigenous people, and we find that these will decrease in 80% of New Guinea's 1030 language areas, with losses of up to 94 species per language area. To mitigate the threats of climate change on the flora, we identify priority sites for protected area expansion that can jointly maximize biodiversity and useful plant conservation.

Psychophysics of the hoverfly: categorical or continuous color discrimination?

There is increasing interest in flies as potentially important pollinators. Flies are known to have a complex visual system, including 4 spectral classes of photoreceptors that contribute to the perception of color. Our current understanding of how color signals are perceived by flies is based on data for the blowfly Lucilia sp., which after being conditioned to rewarded monochromatic light stimuli, showed evidence of a categorical color visual system. The resulting opponent fly color space has 4 distinct categories, and has been used to interpret how some fly pollinators may perceive flower colors. However, formal proof that flower flies (Syrphidae) only use a simple, categorical color process remains outstanding. In free-flying experiments, we tested the hoverfly Eristalis tenax, a Batesian mimic of the honeybee, that receives its nutrition by visiting flowers. Using a range of broadband similar–dissimilar color stimuli previously used to test color perception in pollinating hymenopteran species, we evaluated if there are steep changes in behavioral choices with continuously increasing color differences as might be expected by categorical color processing. Our data revealed that color choices by the hoverfly are mediated by a continuous monotonic function. Thus, these flies did not use a categorical processing, but showed evidence of a color discrimination function similar to that observed in several bee species. We therefore empirically provide data for the minimum color distance that can be discriminated by hoverflies in fly color space, enabling an improved understanding of plant–pollinator interactions with a non-model insect species.

The particle size dependence of the oxygen reduction reaction for carbon-supported platinum and palladium

Model carbon supported Pt and Pd electrocatalysts have been prepared using a high-throughput physical vapor deposition method. For Pt, metal particle sizes are controlled between 1.5-5.5 nm over 100 electrodes of an electrochemical screening chip, allowing the oxygen reduction reaction (ORR) activity of the catalysts to be determined simultaneously. The ORR-specific current density is observed to increase with increasing particle diameter up to approximately 4 nm, at which point the activity begins to level off. The reduction in ORR activity for particles below 4 nm is accompanied by a concomitant increase in the overpotential for surface reduction. The resulting mass activity exhibits a maximum for particles with diameters of approximately 3.5 nm. These results are consistent with results published recently for high area carbon-supported Pt catalysts. For Pd particles, both the specific current density and the mass-specific activity for the ORR are observed to increase with increasing particle diameter, with no distinct optimum observed. The implications for the optimization of Pt- or Pd-based ORR catalysts for proton exchange membrane fuel cell (PEMFC) applications are discussed.

Cytokines and the regulation of apoptosis in reproductive tissues: a review

PROBLEM

To determine the role of apoptosis-regulating genes bax and bcl-2 in reproduction.

METHOD OF STUDY

Review of literature and current data.

RESULTS

The bcl-2 family of apoptotic regulatory gene products interact and form dimers of anti- and pro-apoptotic proteins (e.g., bcl-2 and bax respectively), the ratio of which determines cell death or survival. Menses is associated with increased apoptosis in the glands, a change in bcl-2:bax ratio and increased levels of the pro-apoptotic cytokine TNFalpha. Apoptosis occurs in all placental cell types and increases from first to third trimester. Placental apoptosis is induced by TNFalpha in vitro and increased levels in utero characterize most failing pregnancies, intra-uterine growth restriction (IUGR) and labour. An increased bcl-2:bax ratio and apoptosis in the syncytiotrophoblast characterizes failing first trimester pregnancies. Apoptosis in the syncytiotrophoblast is also associated with IUGR. In a rat model, maternal vitamin A deficiency perturbs fetal development. This is associated with a placental infiltrate of TNFalpha positive neutrophils (day 20) and increased placental apoptosis in areas of infiltration. A similar infiltrate occurs in a mouse model of early pregnancy loss. In the fetal membranes, clusters of bcl-2 negative chorion trophoblast cells undergo apoptosis. This may allow passage of myometrial stimulatory factors that induce labour.

CONCLUSION

The ratio of bcl-2:bax is crucial in the regulation of apoptosis, particularly in the human placenta. Changes in trophoblast apoptosis characterize (1) early pregnancy failure, (2) IUGR and (3) pre-term and term labour. Regardless of gestational age, TNFalpha plays a major role in the induction of placental apoptosis.

Quality of life 5-10 years after primary surgery for oral and oro-pharyngeal cancer

This study reports the quality of life in long-term survivors of oral cancer treated by primary surgery. Two hundred and twenty patients were treated at the Regional Maxillofacial Unit between the years 1987 and 1992, of which 48 were alive and disease free in July 1997. Thirty-eight patients self-completed the following questionnaires: University of Washington Quality of Life Scale (UW-QOL), the European Organisation for Research and Treatment of Cancer (EORTC) core QOQ-C30 (v2) and the EORTC Head and Neck (H&N35). Results for this group were compared with the one year findings of a similar prospective cohort treated in 1995. Long-term survivors tended to report a good or excellent quality of life. Quality of life deficits in the long-term survivors were similar to those at one year. However, a larger longitudinal study is required to test this relationship more rigorously. The similarity of domain scores suggests that quality of life evaluation at one year is a useful marker of long-term outcome.

Analysis of MHC class I expression in equine trophoblast cells using in situ hybridization

Down-regulation of major histocompatibility complex (MHC) genes by trophoblast cells is considered to be a primary mechanism preventing maternal immune rejection of the fetal-placental unit in mammalian pregnancy by rendering these cells, which form the primary barrier between mother and fetus, relatively non-antigenic. In situ hybridization with probes encoding human and horse MHC class I genes was used to characterize the pattern of MHC class I mRNA expression in the various forms of horse trophoblast. Strong hybridization signals were observed in the invasive trophoblast cells of chorionic girdle tissue. In contrast, no hybridization signal specific for MHC class I mRNA transcripts was observed in the descendent endometrial cup trophoblast cells. In the non-invasive trophoblast cells of the allantochorion, no hybridization signals specific for horse MHC class I mRNA transcripts were consistently detected. In parallel to the in vivo results, strong hybridization signals were observed in the small, mononuclear cells present in chorionic girdle cell explant cultures, but not in the population of large binucleate cells corresponding to endometrial cup cells. The results obtained using in situ hybridization are consistent with the hypothesis that expression of MHC class I genes may be controlled at the transcriptional level in horse invasive and non-invasive trophoblast cells, and suggest that down-regulation of MHC class I antigen expression in endometrial cup cells may be accomplished by the same mechanisms in vivo and in vitro.

Differential regulation of melatonin receptors in sheep, chicken and lizard brains by cholera and pertussis toxins and guanine nucleotides

G-proteins define both the pharmacological characteristics and the signalling pathways of G-protein-coupled receptors. Melatonin receptors have been shown to belong to this class of receptors through their sensitivity to modulators of G-protein function. This study reveals that 2-125I-iodomelatonin (125I-MEL) binding to different target tissues is differentially affected by agents which disrupt the G-protein cycle. GTP gamma S, pertussis (PTX) and cholera (CTX) toxins each reduce 125I-MEL binding to ovine pars tuberalis (oPT) and lizard brain membranes, whereas chicken brain is affected only by GTP gamma S (guanosine 5'-O-(3-thiotriphosphate)) and CTX. In contrast, high affinity binding of 125I-MEL in the ovine hippocampus was not affected by any of these agents. This finding, together with the fact that neural binding sites of the sheep brain were found to have markedly lower molecular mass than those of the oPT on native gel electrophoresis (365 vs 525 kDa), suggests that the neural 125I-MEL binding sites in sheep may not be G-protein coupled. Pharmacologically, however, the binding sites in the hippocampus and oPT could not be distinguished using 11 analogues of melatonin. Therefore, these data support the notion not only of multiple forms of melatonin receptor/G-protein complex, but of high affinity binding sites for 125I-MEL which do not display sensitivity to guanine nucleotides.

Role of a children's hospital safety centre in injury control

Over the past 13 years, child safety centres have been established at several Australian Children's hospitals. In a short time, they have developed an important role in community injury control programmes. These centres provide an efficient conduit for transferring up-to-date injury surveillance and prevention information to families, industry, health and education professionals, and government. The activities of the Child Safety Centre at the Royal Children's Hospital in Melbourne are described, together with ways in which a degree of self-funding can be achieved.

Transition from bipolar affective disorder to intermittent Cushing's syndrome: case report

A patient with a 6-year history of bipolar affective disorder who developed cushingoid features during an exacerbation of her psychiatric condition was found to have intermittent hypersecretion of cortisol. Close observation of this patient for 3 years has revealed that her medical and psychiatric symptoms are controlled by suppression of cortisol with bromocriptine.