Trails: an alternative to the field demonstration?

For many students, the traditional field demonstration has several disadvantages. The trail is suggested as an alternative technique, which may be appropriate for students who are not biology specialists, and for senior pupils. The advantages of this method include simpler presentation of information and questions, freedom for the tutor to assist weaker or more questioning students, flexibility in the timing of the exercise, and the need for careful preparation. The use of trails in assessment is suggested. Examples from trails used with Landscape Architecture students are given.     

Production of C2–C4 diols from renewable bioresources: new metabolic pathways and metabolic engineering strategies

C2–C4 diols classically derived from fossil resource are very important bulk chemicals which have been used in a wide range of areas, including solvents, fuels, polymers, cosmetics, and pharmaceuticals. Production of C2–C4 diols from renewable resources has received significant interest in consideration of the reducing fossil resource and the increasing environmental issues. While bioproduction of certain diols like 1,3-propanediol has been commercialized in recent years, biosynthesis of many other important C2–C4 diol isomers is highly challenging due to the lack of natural synthesis pathways. Recent advances in synthetic biology have enabled the de novo design of completely new pathways to non-natural molecules from renewable feedstocks. In this study, we review recent advances in bioproduction of C2–C4 diols, focusing on new metabolic pathways and metabolic engineering strategies being developed. We also discuss the challenges and future trends toward the development of economically competitive processes for bio-based diol production.     

Unemployment rates: an alternative to the Jarman index?

OBJECTIVE--To compare the Jarman index with alternative deprivation measures with regard to its usefulness to district health authorities as an indicator of need at small area level. DESIGN--The Jarman index (UPA (8)), Townsend''s index of material deprivation, the Scottish Development Department''s index, the Department of the Environment''s basic index, and unemployment rates were compared in respect of their correlation with measures of morbidity by electoral ward in a typical English district health authority. Measures of morbidity comprised standardised mortality ratios, admission rates (standardised and non-standardised), and permanent sickness rates. Spearman rank correlation coefficients were calculated for each combination of measures and were then ranked for each of the deprivation indices. SETTING--The 59 electoral wards of the Central Nottinghamshire Health Authority. RESULTS--The Jarman index consistently ranked lower in respect of its correlation with measures of morbidity than did the other deprivation measures. Current unemployment rates correlated well with morbidity measures, in particular with hospital admission rates, with correlations ranging from 0.669 to 0.830 for average and standardised all age admission rates. CONCLUSIONS--The Jarman index seems to be the least appropriate of these indices for health authority use. Unemployment rate merits further consideration as a simple, up to date marker for deprivation and consequent need for health service provision.     

Can resource costs of polyploidy provide an advantage to sex?

The predominance of sexual reproduction despite its costs indicates that sex provides substantial benefits, which are usually thought to derive from the direct genetic consequences of recombination and syngamy. While genetic benefits of sex are certainly important, sexual and asexual individuals, lineages, or populations may also differ in physiological and life history traits that could influence outcomes of competition between sexuals and asexuals across environmental gradients. Here, we address possible phenotypic costs of a very common correlate of asexuality, polyploidy. We suggest that polyploidy could confer resource costs related to the dietary phosphorus demands of nucleic acid production; such costs could facilitate the persistence of sex in situations where asexual taxa are of higher ploidy level and phosphorus availability limits important traits like growth and reproduction. We outline predictions regarding the distribution of diploid sexual and polyploid asexual taxa across biogeochemical gradients and provide suggestions for study systems and empirical approaches for testing elements of our hypothesis.     

Evolutionary Trends in the Flowers of Asteridae: Is Polyandry an Alternative to Zygomorphy?

Background and Aims

Floral symmetry presents two main states in angiosperms, actinomorphy (polysymmetry or radial symmetry) and zygomorphy (monosymmetry or bilateral symmetry). Transitions from actinomorphy to zygomorphy have occurred repeatedly among flowering plants, possibly in coadaptation with specialized pollinators. In this paper, the rules controlling the evolution of floral symmetry were investigated to determine in which architectural context zygomorphy can evolve.

Methods

Floral traits potentially associated with perianth symmetry shifts in Asteridae, one of the major clades of the core eudicots, were selected: namely the perianth merism, the presence and number of spurs, and the androecium organ number. The evolution of these characters was optimized on a composite tree. Correlations between symmetry and the other morphological traits were then examined using a phylogenetic comparative method.

Key Results

The analyses reveal that the evolution of floral symmetry in Asteridae is conditioned by both androecium organ number and perianth merism and that zygomorphy is a prerequisite to the emergence of spurs.

Conclusions

The statistically significant correlation between perianth zygomorphy and oligandry suggests that the evolution of floral symmetry could be canalized by developmental or spatial constraint. Interestingly, the evolution of polyandry in an actinomorphic context appears as an alternative evolutionary pathway to zygomorphy in Asteridae. These results may be interpreted either in terms of plant–pollinator adaptation or in terms of developmental or physical constraints. The results are discussed in relation to current knowledge about the molecular bases underlying floral symmetry.Key words: Floral symmetry, architectural constraints, Asteridae, comparative analysis, composite tree, correlated evolution, evolutionary scenario     

Acanthamoeba: could it be an environmental host of Shigella?

Shigellosis is a serious public health problem in Korea, because large outbreaks of Shigella sonnei infections were recorded in many parts of the country during the period 1998-2000. However, the epidemiological features of shigellosis are not well known. In this study, we devised conditions suitable for the growth and replication of Shigella in an amoebic intracellular environment, and investigate whether medium conditions affect the survival and replication of Shigella within Acanthamoeba. We evaluated the uptake rates of invasive and non invasive S. sonnei strains by three Acanthamoeba species, namely, A. castellanii Neff, A. astronyxis Ray & Hayes, and A. healyi OC-3A. When A. castellanii Neff was infected with S. sonnei 99OBS1 or 80DH248, shigellae was maintained for a longer time in cytoplasms than in other Acanthamoeba species. S. sonnei 99OBS1 strain (a virulent strain) was recovered in higher numbers than the non-virulent S. sonnei 80DH248 strain in all experiments. Moreover, S. sonnei was more easily engulfed by Acanthamoeba at 18 degrees C. The shigellae uptake rates of Neff strain, which was cultured in free-media (less nutrition), were higher (>10-fold) than those observed in original amoeba culture media (PYG medium) in all time points. S. sonnei 99OBS1 was localized, with an intact membrane, to the vacuoles of Acanthamoeba. We conclude that free-living amoebae more likely act as environmental hosts for shigellae, and thus, may have contributed to outbreaks of shigellosis in Korea.     

Alternative signaling pathways: when, where and why?

Alternative cell signal transduction pathways have been demonstrated in some experimental systems. The importance of their existence has not been completely appreciated. In this review we present the cases of alternative pathways resulted from a survey of the available experimental data. The alternative pathways could show different relationships, i.e., synergistic, redundant, additive, opposite and competitive effects. They could have distinct time courses and cell, organ, sex or species specification. Further, they could happen during physiological or pathological situations, and display differentiated sensitivity. These case studies together imply that alternative signal pathways could be involved in the regulation of cell functions at the pathway level. In-depth understanding of the importance of the alternative pathways will rely on building and exploration of mathematical models.     

Probiotics and pharmabiotics: alternative medicine or an evidence-based alternative?

That commensal bacteria play an important role in human health is beyond doubt, and it is now widely accepted that humans function as super organisms, whose collective metabolic potential exceeds the sum of our individual eukaryotic and prokaryotic components. However, while it is has been established that the prokaryotic component of the human superorganism is amenable to manipulation by chemotherapeutic, dietary or microbial interventions, the significance of such alterations in terms of human health or well being is less well established. Prebiotics (non- digestible food ingredients that stimulate the growth and/or activity of bacteria in the digestive system) and probiotics (live microorganisms that when administered in adequate amounts, confer a health benefit on the host) are often bracketed among 'alternative' approaches to influencing human health, such as homeopathy, naturopathy, acupuncture and hypnotherapy. Others believe that prebiotics and probiotics have proven their effectiveness in properly conducted, clinically controlled human trials and therefore can be considered as evidence-based alternatives or adjuncts to conventional medicines. My journey from a position of total skepticism to 'reluctant convert' is the basis of this article, which should not be considered in any sense as a review of the literature but simply a personal account of this transition. While I am not bent on converting other doubters, I will recount some of the thought processes and evidence that has helped to form my current opinion.     

The biosynthesis of monolignols: a "metabolic grid", or independent pathways to guaiacyl and syringyl units?

Lignin is a complex polymer formed by the oxidative polymerization of hydroxycinnamyl alcohol derivatives termed monolignols. The major monolignols in dicotyledonous angiosperm lignin are monomethylated guaiacyl (G) units derived from coniferyl alcohol, and dimethylated syringyl (S) units derived from sinapyl alcohol. The biochemical pathways leading to the formation of monolignols feature successive hydroxylation and O-methylation of the aromatic ring and conversion of the side chain carboxyl to an alcohol function. The current view of the monolignol biosynthetic pathway envisages a metabolic grid leading to G and S units, through which the successive hydroxylation and O-methylation reactions may occur at different levels of side chain oxidation. The present article assesses biochemical and genetic evidence for and against such a model, including recent data on the methylation reactions of monolignol biosynthesis in alfalfa. We draw attention to portions of the currently accepted monolignol pathway that may require revision, and suggest an alternative model in which metabolic channeling allows for independent pathways to G and S lignin.     

Paternal effects on seed germination: a barrier to the genetic assimilation of an endemic plant taxon?

We used a crossing experiment to investigate post-zygotic barriers that might limit introgression between a pair of closely-related, gynodioecious plant species--the widespread weed Silene vulgaris and the local Swedish endemic S. uniflora ssp. petraea. The study not only considered the effects of hybridization on conventionally-used (primary) fitness components such as seed set and progeny survival, but also provided a test for the effects of interspecific hybridization on characters with more subtle or habitat-specific effects on fitness. We detected highly significant paternal effects on seed germination properties, with the germination characteristics of hybrid seed resembling those of the species that served as the pollen donor. These paternal effects on germination represent a potentially strong barrier to interspecific introgression in the two species' natural habitats, where an inappropriate germination response in the habitat of the maternal parent may lead to the failure of seedling establishment. Interspecific crosses had weak or variable effects on progeny survival, flowering and sex ratio, but these effects could not be interpreted in terms of barriers to introgression. Our results indicate that nuclear restorers in S. vulgaris have the capacity to suppress cytoplasmic male-sterility genes in its endemic congener.