Root extracellular traps versus neutrophil extracellular traps in host defence,a case of functional convergence?

The root cap releases cells that produce massive amounts of mucilage containing polysaccharides, proteoglycans, extracellular DNA (exDNA) and a variety of antimicrobial compounds. The released cells – known as border cells or border‐like cells – and mucilage secretions form networks that are defined as root extracellular traps (RETs). RETs are important players in root immunity. In animals, phagocytes are some of the most abundant white blood cells in circulation and are very important for immunity. These cells combat pathogens through multiple defence mechanisms, including the release of exDNA‐containing extracellular traps (ETs). Traps of neutrophil origin are abbreviated herein as NETs. Similar to phagocytes, plant root cap‐originating cells actively contribute to frontline defence against pathogens. RETs and NETs are thus components of the plant and animal immune systems, respectively, that exhibit similar compositional and functional properties. Herein, we describe and discuss the formation, molecular composition and functional similarities of these similar but different extracellular traps.     

Malaria immunity in infants: a special case of a general phenomenon?

Newborn infants in endemic areas are markedly resistant to Plasmodium falciparum malaria. Consequently, severe disease is rare during the first few months of life, and infections tend to be low density and relatively asymptomatic during this period. Although this is generally ascribed to passively transferred immunity, attempts to identify the targets and mechanisms of this protection have been unsuccessful. The implications of the hypothesis that the progression from resistance through susceptibility and back to resistance during infancy and early childhood reflects the gradual acquisition of IgG to variant surface antigens (VSAs), while protection from maternal VSA-specific IgG steadily fades, are discussed here.     

Congenital blepharophimosis and ptosis in a mentally retarded girl: a new case of Ohdo syndrome?

A mentally retarded girl with congenital blepharophimosis, ptosis, abnormal teeth and other features consistent with Ohdo syndrome is reported.     

Hatching in dabbling ducks and emergence in chironomids: a case of predator–prey synchrony?

It has been hypothesized that dabbling ducks (Anas spp.) time breeding to coincide with annual regional peaks in emerging dipterans, especially Chironomidae, which are important prey for newly hatched ducklings. However, this hypothesis has never been evaluated in a replicated lake-level study, including year effects in emergence patterns. We collected duck and invertebrate data from 12 lakes during the nesting seasons 1989–1994 in a watershed in southern Finland. The oligotrophic study lakes are typical of the boreal Holarctic, as are the three focal duck species: mallard Anas platyrhynchos L., widgeon Anas penelope L and teal Anas crecca L. Hatching of ducklings showed a clear peak in relation to ambient phenology (annual ice-out date of lakes), whereas chironomid emergence was more erratic and showed no clear peak at the lake level, although total watershed-level emergence was somewhat higher before and long after the duck hatching peak. Thus, we find no evidence that ducklings hatch in synchrony with abundance peaks of emerging chironomids. There was large within-year temporal variation in chironomid emergence among lakes, but this was not correlated with ambient temperature. The rank of individual lakes with respect to the abundance of emerging chironomids was consistent among as well as within years, a predictability that ought to make adaptive lake choice by ducks possible. On the lake level, there was a positive correlation between the total amount of emerging chironomids and brood use. We argue that emergence patterns of chironomids on typical boreal lakes are neither compressed nor predictable enough to be a major selective force on the timing of egg-laying and hatching in dabbling ducks. Despite spatial (among-lake) patterns of abundance of emerging chironomids being predictable within and among years, the observed pattern of brood use suggests that other factors, e.g. habitat structure, also affect lake choice.     

Malaria morbidity and temperature variation in a low risk Kenyan district: a case of overdiagnosis?

Diagnosis of malaria using only clinical means leads to overdiagnosis. This has implications due to safety concerns and the recent introduction of more expensive drugs. Temperature is a major climatic factor influencing the transmission dynamics of malaria. This study looked at trends in malaria morbidity in the low risk Kenyan district of Nyandarua, coupled with data on temperature and precipitation for the years 2003–2006. July had the highest number of cases (12.2% of all cases) followed by August (10.2% of all cases). July and August also had the lowest mean maximum temperatures, 20.1 and 20.2 °C respectively. April, July and August had the highest rainfall, with daily means of 4.0, 4.3 and 4.9 mm, respectively. Observation showed that the coldest months experienced the highest number of cases of malaria. Despite the high rainfall, transmission of malaria tends to be limited by low temperatures due to the long duration required for sporogony, with fewer vectors surviving. These cold months also tend to have the highest number of cases of respiratory infections. There is a possibility that some of these were misdiagnosed as malaria based on the fact that only a small proportion of malaria cases were diagnosed using microscopy or rapid diagnostic tests. We conclude that overdiagnosis may be prevalent in this district and there may be a need to design an intervention to minimise it.     

The BAR-domain family of proteins: a case of bending and binding?

BAR-domains recently took centre stage in science through a report on the crystal structure of this domain in Drosophila Amphiphysin. Though only weakly conserved at the sequence level, the structure of the BAR domain shows striking similarity to the GTPase-binding domain of Arfaptin 2, an effector of Rho- and Arf- GTPases. On the basis of this sequence and structural similarity, these two proteins have been classified as belonging to the same family, the BAR-domain family, and they probably also have similar functional characteristics. Presented here are the results of a database search for the sequence of the BAR domain of Amphiphysin and Arfaptin 2. This search identified a variety of related proteins, most of which are involved in intracellular transport and especially in endocytosis. For example, the BAR-domain family includes Endophilins, GTPase-activating proteins of the Centaurinbeta family and Oligophrenins, the adaptor proteins APPL1 and APPL2 that were recently shown to interact with the small GTPase Rab5, as well as members of the Sorting nexin family. On the basis of the structures of Amphiphysin and Arfaptin 2 and the cellular role of Amphiphysins in the early steps of endocytosis, the functions of the BAR domain have been defined as a dimerization motif and as sensing and inducing membrane curvature. However, data on Arfaptin 2 and now also on the Adaptor proteins APPL1 and 2 suggest that another function of the BAR domain is to bind to small GTPases.     

MARCKS: a case of molecular exaptation?

MARCKS (myristoylated alanine-rich C kinase substrate, 32 kDa) and its 20 kDa brother MARCKS-related protein (MRP) are abundant, widely distributed proteins unusually rich in alanine and glutamic acid, and with lysines, serines and phenylalanines concentrated in a compact "effector domain" (ED) near the middle of the sequence. Its conformation in solution appears to be labile, with little evidence for definite secondary structure. MARCKS (and MRP) interact inter alia with lipid bilayer membranes (via the myristoyl group and the ED), with protein kinases (which phosphorylate the serines in the ED), and with calmodulin (via the ED); synergies between these diverse interactions present an unusually rich array of possibilities for a variety of regulatory r?les. The proteins appear to be essential for controlling cell shape changes, possibly via involvement in cytoskeleton-membrane linkage. MRP deficiency leads to neural tube defects in brain development; MARCKS overexpression strongly depresses the proliferation of cancer cells.     

Are corticosterone levels a good indicator of food availability and reproductive performance in a kittiwake colony?

We evaluated the use of corticosterone to gauge forage availability and predict reproductive performance in black-legged kittiwakes (Rissa tridactyla) breeding in Alaska during 1999 and 2000. We modeled the relationship between baseline levels of corticosterone and a suite of individual and temporal characteristics of the sampled birds. We also provided supplemental food to a sample of pairs and compared their corticosterone levels with that of pairs that were not fed. Corticosterone levels were a good predictor of forage availability in some situations, although inconsistencies between corticosterone levels and reproductive performance of fed and unfed kittiwakes suggested that this was not always the case. In general, higher corticosterone levels were found in birds that lacked breeding experience and in birds sampled shortly after arriving from their wintering grounds. All parameters investigated, however, explained only a small proportion of the variance in corticosterone levels. We also investigated whether corticosterone, supplemental feeding, year of the study, breeding experience, body weight, and sex of a bird were able to predict laying, hatching, and fledging success in kittiwakes. Here, breeding experience, year of the study, and body weight were the best predictors of a bird's performance. Corticosterone level and supplemental feeding were good predictors of kittiwake reproductive performance in some cases. For example, corticosterone levels of birds sampled during the arrival stage reliably predicted laying success, but were less reliable at predicting hatching and fledging success. Counts of active nests with eggs or chicks may be more reliable estimates of the actual productivity of the colony. Supplemental feeding had strong effects on kittiwake productivity when natural forage was poor, but had little effect when natural forage was plentiful.     

Cultural evolution and the social sciences: a case of unification?

This paper addresses the question of how to understand the relationship between Cultural Evolutionary Science (CES) and the social sciences, given that they coexist and both study cultural change. I argue that CES is best understood as having a unificatory or integrative role between evolutionary biology and the social sciences, and that it is best characterized as a bridge field; I describe the concept of a bridge field and how it relates to other non-reductionist accounts of unification or integration used in the philosophy of science literature.     

Somatic embryogenesis in conifers—A case study of induction and development of somatic embryos in Picea abies

Vegetatively propagated material offers many advantages over seed material in forest tree breeding research and in reforestation programmes. Evidence is accumulating to suggest that using somatic embryos in forestry is a viable option. However, before somatic embryos can be used optimally in forestry, basic research aimed at increasing the number of responsive genotypes as well as the age of the primary explant is needed. This in turn requires the establishment of a basic understanding of the physiological and molecular processes that underlie the development of somatic embryos. The functions of genes and their developmental and tissue specific regulation are studied using transient and stable transformation techniques.The process of somatic embryogenesis can be divided into different steps: (1) initiation of somatic embryos from the primary explant, (2) proliferation of somatic embryos, (3) maturation of somatic embryos and (4) plant regeneration. Cortical cells in the primary explant are stimulated to go through repeated divisions so that dense nodules are formed from which somatic embryos differentiate. The first formed somatic embryos continue to proliferate and give rise to embryogenic cell lines. Embryogenic cell lines of Picea abies can be divided into two main groups A and B, based on morphology, growth pattern and secretion of proteins. Our results suggest that extracellular proteins play a crucial role in embryogenesis of Picea abies. Somatic embryos from group A can be stimulated to go through a maturation process when treated with abscisic acid. Mature somatic embryos can develop into plants.Abbreviations ABA abscisic acid - BA N⁶-benzyladenine - 2,4-D dichlorophenoxy acetic acid     

Perturbed reproductive development in salt-treated Sorghum bicolor: a consequence of modifications in regulation networks?

In Sorghum bicolor, tolerance to salinity is improved by a 3-week treatment with 150 mM NaCl during early vegetative development. However, a strong decrease in fertility is also observed, suggesting that reproductive development becomes perturbed by this adaptive response to salinity. This study is an attempt to clarify the origin of such a paradoxical phenomenon. The relationships between end-cycle characters are modified by the NaCl treatment: some linkages disappear, while others are strengthened, especially those linking fertility with plant height. In parallel, a transient reduced level of linkage between leaf characters is observed around the unfolding of the eighth to the tenth leaves, defining a critical period in vegetative development separating two discrete phases. A relationship is observed between events occurring during this short critical period and the NaCl-induced perturbations in fertility. This suggests that reproductive development is conditioned by the influence of salinity on events occurring during a short period of vegetative development, independently of the level of tolerance to salinity quantified by the rate of vegetative growth.     

What's in a name? The case of cyanobacteria

A redefinition of the cyanobacterial lineage has been proposed based on phylogenomic analysis of distantly related nonphototrophic lineages. We define Cyanobacteria here as “Organisms in the domain bacteria able to carry out oxygenic photosynthesis with water as an electron donor and to reduce carbon dioxide as a source of carbon, or those secondarily evolved from such organisms.”     

Decision-making in variable environments-- a case of group selection and inter-generational conflict?

Suppose organisms need to engage in a particular action exactly once during some fixed period of time. Further suppose they can time this action to optimise their fitness based on the expected current payoff and the probability distribution of later payoffs. For an example we consider the timing of the annual nuptial flight in eusocial insects. Using two population genetics models, we ask whether stochasticity leads to evolutionary conflict between the queen and her offspring. We find that the winning phenotype is independent of who controls the timing. The best response to any non-equilibrium population strategy is the same in both control scenarios, a result that carries over to the diploid case. Although inter-generational conflict is therefore ruled out, the models support a previous observation that at equilibrium some of the offspring have a lower expected payoff than others. By measuring fitness in terms of relative reproductive success, we show that all individuals are in fact equally well off making group-selectionist arguments unnecessary. As such, the models should improve our understanding of the difficult conceptual problem of the unit of natural selection in stochastic environments.     

Mesenchymal stromal cells and fibroblasts: a case of mistaken identity?

The plastic-adherent fibroblast-looking cells that can be isolated and culture-expanded from bone marrow and many other tissues are widely known as mesenchymal stromal cells (MSC). In addition to their fibroblast-like morphology, they are characterized by a panel of cell-surface markers and their potential to differentiate into bone, fat and cartilage. Based on their intriguing immunomodulatory and regenerative properties, MSC are being investigated as cellular therapeutics for a variety of clinical indications. However, many questions regarding the true identity and functionality of these cells in vivo remain unanswered. Fibroblasts, known for a much longer time but still poorly characterized, are also considered to be a ubiquitous stromal element of almost all tissues and are believed to play a role in tissue homeostasis. Despite the presence of MSC and fibroblasts in almost all tissues, similar morphology and other shared characteristics, the exact relationship between MSC and fibroblasts has remained undetermined. In this review, based on recent and old, but often neglected, literature it is suggested that ex vivo culture-expanded MSC and fibroblasts are indistinguishable by morphology, cell-surface markers, differentiation potential and immunologic properties.     

Assumption validity in human optimal foraging: The Barí hunters of Venezuela as a test case

Optimal foraging theory is being used increasingly as a means of understanding human foraging behavior. One of the central assumptions of optimal foraging theory is that prey items or patches are encountered sequentially and as a Poisson process. Using empirical data gathered on the Barí hunters of Venezuela, we assess the validity of this central assumption. We compare our observed distribution of encounter frequencies with an expected Poisson distribution, utilizing chisquare tests and graphic representations. The results are strikingly consonant with the expected Poisson distribution and lend support to the applicability of optimal foraging models to human hunting behavior.     

The serpent and the egg: unidirectional evolution of reproductive mode in vipers?

Dollo’s law, that complex characters are not regained in evolution, is a pattern applied to many systems. Recent work has evaluated unidirectional evolution in a number of contexts, and several violations of this law have been documented. These methods have also been criticized for potentially overestimating reversals. We test the hypothesis that the ancestral reproductive mode of oviparity can be regained in vipers, in opposition to Dollo’s law. We use model comparison and ancestral character state reconstruction methods that address recent criticisms, and find evidence both supporting and refuting Dollo’s predictions from different analyses. We discuss our results in the context of unidirectional evolution and review factors required for strong inference of violations of Dollo’s law.     

Xenotransplantation: a tool for reproductive biology and animal conservation?

The transplantation of reproductive organs, including ovaries and ovarian tissue, was pioneered over 100 years ago. In the 1960s, ovarian grafting was used as a tool to investigate ovarian function, but with the recent development of more effective cryopreservation protocols for ovarian tissue, germline preservation and propagation have now become realistic goals. This review describes progress in ovarian banking and ovarian tissue transplantation, with emphasis on how fresh and frozen ovarian tissue can be used in assisted reproduction for both humans and animals. This paper focuses most closely on the potential value of xenotransplantation, the transplantation of gonads from one species to another, to conserve rare and endangered species. Specific attention is drawn to the use of xenotransplantation as a strategy for generating viable gametes that can be used to produce live fertile offspring. Other upcoming xenogeneic technologies that may be of potential significance in animal conservation, such as transplantation of whole ovaries or isolated growing follicles, and even male germ cells, are discussed.     

Evolution of alternative male morphotypes in oxyurid nematodes: a case of convergence?

Male dimorphism has been reported across different taxa and is usually expressed as the coexistence of a larger morph with exaggerated male traits and a smaller one with reduced traits. The evolution and maintenance of male dimorphism are still poorly understood for several of the species in which it has been observed. Here, we analyse male dimorphism in several species of reptile parasitic nematodes of the genus Spauligodon, in which a major male morph (exaggerated morph), which presents the traditional male morphological traits reported for this taxon, coexists with a minor morph with reduced morphological traits (i.e. reduced genital papillae) resembling more closely the males of the sister genus Skrjabinodon than Spauligodon major males. Because of the level of uncertainty in the results of ancestral state reconstruction, it is unclear if the existence of male dimorphism in this group represents independent instances of convergent evolution or an ancestral trait lost multiple times. Also, although the number of major males per host was positively correlated with the number of females, the same did not hold true for minor males, whose presence was not associated with any other ecological factor. Nevertheless, the existence of male dimorphism in Spauligodon nematodes is tentatively interpreted as resulting from alternative reproductive tactics, with differences in presence and number of individuals as indicators of differences in fitness, with the lower numbers of minor males per host likely maintained by negative frequency‐dependent selection.     

Latitudinal patterns of reproductive effort in gamebirds and waterfowl: bucking the trend?

Clutch sizes of gamebirds decrease in a hyperbolic fashion towards the equator, but their clutch investment (total clutch mass as a proportion of female body weight) does not vary with latitude, regardless of whether body mass and phylogeny are factored out. In contrast, clutch sizes of wildfowl increase towards the tropics, but when corrected for body mass and phylogeny, no latitudinal pattern remains. Clutch investment by wildfowl peaks in the tropics, but this relationship becomes insignificant when body size and phylogeny are factored out. These contrasting patterns are explored in terms of habitat type, and the groups’ shared precocial development mode.