The C : N : P stoichiometry of autotrophs – theory and observations

Evolution has set biochemical constraints on the chemical composition of living organisms. These constraints seem to lead to increases in N : C and P : C ratios with increasing relative growth rate for all types of organisms. The N : P ratio also seems to decrease with relative growth rate for heterotrophs whereas autotrophs may show a more complex behaviour. Here I will show that, from biochemical considerations, N : C should increase linearly and P : C quadratically with relative growth rate in autotrophs with the consequence that N : P increases at low relative growth rates, passes a maximum and then decreases at high relative growth rates. These predictions are verified against observations for a freshwater alga (Selenastrum minutum) and a tree seedling (Betula pendula). Changes in temperature, light or other factors that affect the growth rate of autotrophs interact with nutrient supply in such a way that there are no simple rules for as to how N : P will change.     

The Occurrence and Economic Impact of <Emphasis Type="Italic">Plasmodiophora brassicae</Emphasis> and Clubroot Disease

The significance of Plasmodiophora brassicae Woronin and clubroot disease which it incites in members of the family Brassicaceae is reviewed as the focus for this special edition of the Journal of Plant Growth Regulation. This is a monographic treatment of recent research into the pathogen and disease; previous similar treatments are now well over half a century old. Vernacular nomenclature of the disease indicates that it had a well-established importance in agriculture and horticulture from at least the Middle Ages onward in Europe and probably earlier. Subsequently, the pathogen probably spread worldwide as a result of transfer on and in fodder taken by colonists as livestock feed. It is a moot point, however, whether there was much earlier spread by P. brassicae into China and subsequently Japan as Brassica rapa (Chinese cabbage and many variants) colonized those lands in archaeological time. Symptoms, worldwide distribution, and economic impact are briefly described here to provide a basis for understanding subsequent papers. Clubroot disease devastates both infected field and protected vegetable and agricultural Brassica crops. Particular importance is placed on recent reports of crop losses in tropical countries, albeit where the crops are grown in cooler altitudes, and in the Canadian prairie land canola crops. The latter is of enormous importance because this crop is the single most important and essential source of vegetable oils used in human foodstuffs and in industrial lubricants where mineral oils are inappropriate.     

Serum Nutritional Profiles of Free-Ranging <Emphasis Type="Italic">Alouatta Caraya</Emphasis> in Northern Argentina: Lipoproteins; Amino Acids; Vitamins A,D, and E; Carotenoids; and Minerals

Quantifying circulating nutrient concentrations in sera of free-ranging subjects will help to establish a basis from which we can evaluate the nutritional status and needs of the captive population. We collected serum samples from 26 free-ranging black-and-gold howlers (Alouatta caraya) in San Cayetano forest in northern Argentina. We analyzed them for concentrations of lipoproteins; amino acids; vitamins A, D, and E; carotenoids; and minerals. There are a few significant differences between sexes in concentrations of high-density lipoprotein cholesterol, certain amino acids, vitamin E, lutein + zeaxanthin, and copper. Most nutritional parameters are similar to the ones measured in free-ranging Mexican mantled howlers (Alouatta palliata mexicana) and in captive New World primates (NWPs). Carotenoid, vitamin D, and phosphorus concentrations are the exceptions. Carotenoid concentrations are higher in free-ranging Alouatta caraya than reported for other free-ranging and captive species. Vitamin D concentrations are 14 times greater in the free-ranging black-and-gold howlers than in captive NWPs. Phosphorus concentrations are also higher than expected and higher than typically occur in captive primates, leading to a 1:1.6 calcium:phosphorus ratio. Because we based our study on a small number of free-ranging howlers, additional samples from different regions and throughout the year would better define desirable nutritional parameters for captive howlers.     

Reproductive ‘Surrogacy’ and Parental Licensing

A serious moral weakness of reproductive ‘surrogacy’ is that it can be harmful to the children who are created. This article presents a proposal for mitigating this weakness. Currently, the practice of commercial ‘surrogacy’ operates only in the interests of the adults involved (the gestator and the commissioning individuals who employ her), not in the interests of the child who is created. Whether ‘surrogacy’ is seen as the purchase of a baby, the purchase of parental rights, or the purchase of reproductive labor, all three views share the same significant flaws. They endorse the transfer, for a fee, of the infant from the woman who gestated it to those who commissioned it, but without justifying such a transfer; they fail to demonstrate that the commissioners have any entitlement to the infant, or, for that matter, suitability to be the infant's parents; and they fail to take any notice of the infant's needs, interests, and wellbeing. A mere genetic connection is not enough to establish that the commissioners are entitled to receive the baby or that they are competent to raise it. Their good intentions, however caring, are not enough. Therefore, just as in the practice of adoption, there should be a formal institutionalized system for screening and licensing the prospective social parents, which would make the infant's needs, interests, and wellbeing paramount. I reply to several potential objections to this proposal, including the objection that genetic parents who raise their own child are not screened and licensed.     

Diversity and recombination in <Emphasis Type="Italic">Wolbachia</Emphasis> and <Emphasis Type="Italic">Cardinium</Emphasis> from <Emphasis Type="Italic">Bryobia</Emphasis>spider mites

BACKGROUND: Wolbachia and Cardinium are endosymbiotic bacteria infecting many arthropods and manipulating host reproduction. Although these bacteria are maternally transmitted, incongruencies between phylogenies of host and parasite suggest an additional role for occasional horizontal transmission. Consistent with this view is the strong evidence for recombination in Wolbachia, although it is less clear to what extent recombination drives diversification within single host species and genera. Furthermore, little is known concerning the population structures of other insect endosymbionts which co-infect with Wolbachia, such as Cardinium. Here, we explore Wolbachia and Cardinium strain diversity within nine spider mite species (Tetranychidae) from 38 populations, and quantify the contribution of recombination compared to point mutation in generating Wolbachia diversity. RESULTS: We found a high level of genetic diversity for Wolbachia, with 36 unique strains detected (64 investigated mite individuals). Sequence data from four Wolbachia genes suggest that new alleles are 7.5 to 11 times more likely to be generated by recombination than point mutation. Consistent with previous reports on more diverse host samples, our data did not reveal evidence for co-evolution of Wolbachia with its host. Cardinium was less frequently found in the mites, but also showed a high level of diversity, with eight unique strains detected in 15 individuals on the basis of only two genes. A lack of congruence among host and Cardinium phylogenies was observed. CONCLUSIONS: We found a high rate of recombination for Wolbachia strains obtained from host species of the spider mite family Tetranychidae, comparable to rates found for horizontally transmitted bacteria. This suggests frequent horizontal transmission of Wolbachia and/or frequent horizontal transfer of single genes. Our findings strengthens earlier reports of recombination for Wolbachia, and shows that high recombination rates are also present on strains from a restrictive host range. Cardinium was found co-infecting several spider mite species, and phylogenetic comparisons suggest also horizontal transmission of Cardinium among hosts.     

A comparison of the autecology of two seed-taking ant genera, <Emphasis Type="Italic">Rhytidoponera</Emphasis> and <Emphasis Type="Italic">Melophorus</Emphasis>

Members of the genus Rhytidoponera and, to a lesser extent, certain Melophorus spp. are keystone mutualists for the dispersal of seeds in the southwest of Western Australia, with important ramifications for the ecology and speciation of plants in this biodiversity hotspot. For this reason, it is important to understand the autecology of the relevant ant species and the way in which they interact with plant seeds. This paper addresses key aspects of the ecology of three such ant species, Rhytidoponera violacea (Forel), R. inornata Crawley and Melophorus turneri perthensis Wheeler. Data are presented on their geographic distribution, seasonality of foraging, diurnal activity, response to fire, nest site preference, nest structure, colony size, feeding habits, foraging response to seed availability, and seedling emergence from nests. The role of all three species as seed dispersers is confirmed, and all three species have ecologies that are well-suited for dispersal and survival of native plant seeds. Preservation of this interaction is important for the conservation of plants, and it is fortuitous that all three species are able to survive disturbance and return to rehabilitated areas. However, the smaller R. inornata, and to a lesser extent, the larger R. violacea, are vulnerable to invasive ant [Pheidole megacephala (Fabricius)] incursions. M. turneri perthensis is able to coexist with the invasive ant unless this is at high densities, probably as a result of its ability to forage during high temperatures when the invasive species is inactive.     

The systems V<Superscript>IV</Superscript>O<Superscript>2+</Superscript>-glutathione and related ligands: a potentiometric and spectroscopic study

The equilibria in the system V(IV)O(2+)-glutathione in aqueous solution were studied in the pH range 2-11 by a combination of pH-potentiometry and spectroscopy (EPR, visible absorption and circular dichroism). The results of the various methods are consistent and the equilibrium model includes the species MLH(3), MLH(2), MLH, ML(2)H(2), MLH(-1), and MLH(-2) and several hydrolysis products (where H(4)L denotes totally protonated glutathione); individual formation constants and spectra are given. ML(2)H(2) is the predominant species at physiological pH. Plausible structures for each stoichiometry are discussed. The related V(IV)O(2+) systems of S-methylglutathione and gamma- L-glutamyl- L-cysteinyl ethyl ester were studied by means of the same spectroscopic techniques in order to support the established binding modes for the glutathione complexes. The importance of glutathione and oxidized glutathione in binding V(IV)O(2+) in cells is assessed.     

Thermal limits of wild and laboratory strains of two African malaria vector species, <Emphasis Type="Italic">Anopheles arabiensis</Emphasis> and <Emphasis Type="Italic">Anopheles funestus</Emphasis>

ABSTRACT: Malaria affects large parts of the developing world and is responsible for almost 800,000 deaths annually. As climates change, concerns have arisen as to how this vector-borne disease will be impacted by changing rainfall patterns and warming temperatures. Despite the importance and controversy surrounding the impact of climate change on the potential spread of this disease, little information exists on the tolerances of several of the vector species themselves. METHODS: Using a ramping protocol (to assess critical thermal limits - CT) and plunge protocol (to assess lethal temperature limits - LT) information on the thermal tolerance of two of Africa's important malaria vectors, Anopheles arabiensis and Anopheles funestus was collected. The effects of age, thermal acclimation treatment, sex and strain (laboratory versus wild adults) were investigated for CT determinations for each species. The effects of age and sex for adults and life stage (larvae, pupae, adults) were investigated for LT determinations. RESULTS: In both species, females are more tolerant to low and high temperatures than males; larvae and pupae have higher upper lethal limits than do adults. Thermal acclimation of adults has large effects in some instances but small effects in others. Younger adults tend to be more tolerant of temperature changes than older age groups. Long-standing laboratory colonies are sufficiently similar in thermal tolerance to field-collected animals to provide reasonable surrogates when making inferences about wild population responses. Differences between these two vectors in their thermal tolerances, especially in larvae and pupae, are plausibly a consequence of different habitat utilization. CONCLUSIONS: Limited plasticity is characteristic of the adults of these vector species relative to others examined to date, suggesting limited scope for within-generation change in thermal tolerance. These findings and the greater tolerance of females to thermal extremes may have significant implications for future malaria transmission, especially in areas of current seasonal transmission and in areas on the boundaries of current vector distribution.     

Kinematic and Dynamic Characteristics of Pulsating Flow in 180^o Tube

Kinematic and dynamic characteristics of pulsating flow in a model of human aortic arch are obtained by a computational analysis. Three-dimensional flow processes are summarized by pressure distributions on the symmetric plane together with velocity and pressure contours on a few cross sections for systolic acceleration and deceleration. Without considering the effects of aortic tapering and the carotid arteries, the development of tubular boundary layer with centrifugal forces and pulsation are also analyzed for flow separation and backflow during systolic deceleration.     

Urbanisation induces early flowering: evidence from <Emphasis Type="Italic">Platanus acerifolia</Emphasis> and <Emphasis Type="Italic">Prunus cerasus</Emphasis>

The effect of towns on plant phenology, i.e. advancement of spring development compared with a rural environment, via the urban heat island (UHI) phenomenon, has been shown for many towns in many countries. This work combines experimental and observational methodology to provide a better and deeper view of climatic habitat in an urban context with a view to understanding the relationship between plant development and urban climate on the intra-urban scale (by taking into account town structure). A dense network of 17 meteorological stations was set up in Rennes, France, enabling us to identify and quantify climatic changes associated with the UHI. Meanwhile, phenological observations were made during early spring (March and April) in 2005 on Platanus acerifolia and Prunus cerasus to study the relationship between climatic and phenological data. The results show that there is both a climatic gradient and a developmental gradient corresponding to the type of urbanisation in the town of Rennes. The town influences plant phenology by reducing the diurnal temperature range and by increasing the minimum temperature as one approaches the town centre. The influence of ground cover type (plants or buildings) on development is also shown. The developmental phases of preflowering and flowering are influenced to differing extents by climatic variables. The period during which climatic variables are effective before a given developmental phase varies considerably. The preflowering phases are best correlated with the mean of the minimum air temperature for the 15-day period before the observation, whereas flowering appears to be more dependent on the mean of the daily diurnal temperature range for the 8 days preceding the observation.     

The dynamic transfer of <Superscript>3</Superscript>H and <Superscript>14</Superscript>C in mammals: a proposed generic model

Associated with the present debate regarding the potential revival of nuclear energy there is an increased interest in assessing the radiological risk to the public and also the environment. Tritium and ¹⁴C are key radionuclides of interest in many circumstances (e.g. heavy water reactors, waste storage and fusion reactors). Because the stable analogues of these two radionuclides are integral to most biological compounds, their modelling should follow general principles from life sciences. In this paper, a model of the dynamics of ¹⁴C and ³H in mammals is proposed on the basis of metabolic understanding and of, as far as possible, readily available data (e.g. for organ composition and metabolism). The model is described together with validation tests (without calibration) for a range of farm animals. Despite simplifications, the model tests are encouraging for a range of animal types and products (tissues and milk), and further improvements are suggested.     

Changing ecology of Lake Victoria cichlids and their environment: evidence from C<Superscript>13</Superscript> and N<Superscript>15</Superscript> analyses

Springs are spatially restricted and insular ecotones. In the Alps, topography enhances this isolation. Springs are to a certain extent inhabited by organisms which are adapted to the relatively constant environmental conditions in springs. We examined thirty-six springs in eight different areas in the Swiss National Park (SNP) to understand if the macroinvertebrate assemblages of high-elevation springs are isolated or interconnected communities. We quantitatively and qualitatively sampled the macroinvertebrate assemblages of the springs and monitored environmental parameters. The similarity of the macroinvertebrate assemblages of the springs within and the dissimilarities between the different areas were relatively high; a clear spatial isolation was not evident. The differences of macroinvertebrate assemblages in different areas were explained by substrate parameters: springs in areas at lower altitudes were characterized by organic substrates and many water mite species. High-elevation springs were characterized by coarse inorganic substrates and Trichoptera of the genus Drusus. For spring conservation, it is important to decide on an individual basis if the loss of a single spring will have severe consequences for spring biodiversity.     

<Emphasis Type="Bold">Intersex Activists in Israel: Their Achievements and the Obstacles They Face</Emphasis>

This article focuses on the dynamic between the medical policy on intersex bodies and intersex activists in Israel. Recently, in many countries changes have taken place in medical guidelines regarding intersex patients and laws that regulate medical practices and prohibit irreversible surgeries for intersex babies for cosmetic reasons and without the patient’s consent. In Israel, intersex activists are limited by several factors. On the one hand, they are influenced by the achievements of intersex activism around the world but on the other, the pathologizing medical discourse and socio-medical practices, which include early diagnosis, early irreversible surgeries, and secrecy surrounding intersexed bodies, present obstacles to achieving bodily autonomy for intersex individuals and social recognition of different sex development. Nevertheless, intersex activists are attempting to find different social and media spaces in which to achieve public acknowledgement and future bodily autonomy for intersexed people and seeking medical professionals’ cooperation. Recently, the Israeli Ministry of Health published a new circular for intersex/DSD patients, and while it does not clearly forbid irreversible surgeries, it provides information about the complexities of intersex people and their experience.     

Responses of the ciliates <Emphasis Type="Italic">Tetrahymena</Emphasis> and <Emphasis Type="Italic">Paramecium</Emphasis> to external ATP and GTP

The unicellular ciliates Paramecium and Tetrahymena are the simplest eukaryotic cells to show reliable depolarizing responses to micromolar concentrations of external ATP and GTP. Their simplicity allows for combined analysis of swimming behavior, electrophysiology, receptor binding, behavioral mutant and drug screens as well as molecular genetic approaches such as RNAi and gene knockouts experiments. ATP and GTP are depolarizing chemorepellents in both ciliates, producing measurable receptor potentials and Ca²⁺-based action potentials that are correlated with jerking behaviors called avoiding reactions (AR). GTP also causes repetitive continuous ciliary reversals (CCR) and oscillating plateau depolarizations in Paramecium. Both ciliates show high affinity, saturable external binding of ³²P-GTP and ³²P-ATP but GTP does not compete for ATP binding and vice versa. Chemosensory adaptation occurs after continued exposure (15 min) to these ligands, producing a loss of external binding and forward swimming. However, cells adapted to ATP still bind and respond to GTP and GTP-adapted cells still bind and respond to ATP. This, combined with pharmacological analyses, suggests that there are two separate receptor systems: A metabotropic ATP receptor pathway and a different, novel GTP receptor pathway. A Paramecium mutant (ginA) lacks the GTP-induced oscillating depolarizations but does show AR in GTP, unveiling isolated GTP-receptor potentials for study. An ecto-ATPase is also present that may be involved in inactivation of ATP and GTP signals. Gene knockout experiments are currently underway to determine the roles of the ecto-ATPase and a putative 7-transmembrane spanning receptor in these responses.     

Analysis of a <Emphasis Type="Italic">c</Emphasis><Subscript>0</Subscript><Emphasis Type="Italic">t-1</Emphasis> library enables the targeted identification of minisatellite and satellite families in <Emphasis Type="Italic">Beta vulgaris</Emphasis>

Background  

Repetitive DNA is a major fraction of eukaryotic genomes and occurs particularly often in plants. Currently, the sequencing of the sugar beet (Beta vulgaris) genome is under way and knowledge of repetitive DNA sequences is critical for the genome annotation. We generated a c ₀ t-1 library, representing highly to moderately repetitive sequences, for the characterization of the major B. vulgaris repeat families. While highly abundant satellites are well-described, minisatellites are only poorly investigated in plants. Therefore, we focused on the identification and characterization of these tandemly repeated sequences.     

<Emphasis Type="Italic">Trans</Emphasis>-translation: Findings and hypotheses

Trans-translation is a unique process that switches the synthesis of a polypeptide hain encoded by a nonstop mRNA to the mRNA-like domain of tmRNA. The process is used in bacterial cells for rescuing the ribosomes arrested during translation of nonstop mRNA and directing this mRNA and the polypeptide product for degradation. Activity of tmRNA is essential for bacterial survival under adverse conditions, the quality control of translation, and the regulation of certain physiological pathways. The review focuses on recent advances in trans-translation studies. Details of the tmRNA-SmpB interaction and the structures of early ribosomal complexes are characterized, the causes of the appearance of an empty A site in the translating ribosome and possible mechanisms of the stalled ribosome recognition and resume codon determination are discussed, and the proteins degrading nonstop mRNAs and tagged peptides are considered.     

Predicted and verified distributions of <Emphasis Type="Italic">Ateles geoffroyi</Emphasis> and <Emphasis Type="Italic">Alouatta palliata</Emphasis> in Oaxaca,Mexico

Primate conservation requires a better knowledge of the distributions and statuses of populations in both large areas of habitat and in areas for which we currently have no information. We focused on spider monkeys (Ateles geoffroyi) and howler monkeys (Alouatta palliata) in the state of Oaxaca, Mexico. This Mexican state has protected large tracts of forest, and has historical records for both primates, although very little is known about them. To update our knowledge of the distributions of these primates and identify potential areas in which they are present, we modeled their geographic distributions by characterizing their ecological niches using the genetic algorithm for rule-set production (GARP), performed interviews and carried out field surveys. The predicted distributions, surveys and interviews indicate that the distributions of these primates are restricted to northeastern Oaxaca. The results suggest that spider monkeys occupy a wider area and elevational range than howler monkeys. Throughout that range there is a wide variety of suitable habitats for these primates. Most of the sites where monkeys were recorded in the field are not officially protected and there was evidence of hunting and habitat destruction. It is important to improve protection, economic alternatives and environmental education as we move towards an integral solution for the conservation of these species. Validation of the GARP model was done for A. geoffroyi, since we had obtained enough field data for this species; this validation indicated that the predicted distribution of the species was statistically better than expected by chance. Hence, ecological niche modeling is a useful approach when performing an initial assessment to identify distribution patterns, detecting suitable areas for future exploration, and for conservation planning. Our findings provide an improved basis for primate conservation and productive fieldwork in Oaxaca.