A fresh look at the open rhinoplasty technique

Use of the open rhinoplasty technique (ORT) in certain nasal and septal deformities has proven to be an invaluable asset in the rhinoplasty armamentarium of the authors. Primarily owing to the markedly increased exposure with this technique, more accurate assessment of the deformities is possible and additional or improved surgical maneuvers become available, particularly in the tip. Sculpting the entire cartilaginous and/or bony vault, as well as correcting difficult septal malalignments, can be carried out under better direct vision with greater precision, accuracy, and predictability. This has led to improved and more consistent final results. Previous criticisms of unsightly columellar scars have been virtually eliminated through the use of improved surgical techniques and simple magnification. Overall, open rhinoplasty technique can provide many distinct advantages in certain nasal deformities with no real disadvantages over conventional closed techniques.     

A fresh look at an antiviral helicase

In order to survive, all organisms must guard against viral infections. Recognition of viruses is accomplished via multiple sensors. Many mammalian proteins can recognize viral products, such as double-stranded RNA （dsRNA）, yet few of them are known to induce interferon, the central antiviral messenger. Since interferon is indispensable for successful antiviral defense [1], the interferon-inducing sensors have been of particular interest. However, a clear understanding of such sensors has been elusive, and the first well-established sensor family, the toll-like receptors （TLRs）, was described relatively recently [2]. Antiviral TLRs are positioned in the endosomes, where they report the appearance of viral genetic material （DNA, single-and double-stranded RNA）. However, the question of potential virus sensors in the cytoplasm was left open. Given the particular effectiveness ofintracellular dsRNA at inducing interferon, it was suspected that dsRNA-binding sensor molecules would be found in the cytoplasm.[第一段]     

A fresh look at the temporal dynamics of binocular rivalry

Human observers viewed dichoptic orthogonal sine-wave gratings and indicated when exclusive visibility occurred in either eye. Contrast was held constant in one eye and was increased or decreased in the other eye for a number of alternation cycles (continuous presentation) or for only the duration of a single period of exclusive visibility (synchronous presentation). The synchronous presentation condition allowed us to identify the differing effects of contrast during the suppressed and during the dominant periods. Mixed phases were recorded as distinct from suppressed and dominant phases, and new classifications of compound-dominant and compound-suppressed phases are defined. The results indicate that binocular rivalry responds to stimulus contrast in two ways. 1) The duty-cycle of dominance and suppression is determined by the relative image contrast between the two eyes, with dominance of the higher contrast image being favored, and 2) the overall rate of alternation is driven by monocular image contrast during the suppressed phase (increased monocular contrast increases the alternation rate) and to a lesser extent by monocular contrast during the dominant phase (increased monocular contrast decreases the rate). A model is developed to reflect these ideas. These results support a reciprocal inhibition oscillator as the underlying mechanism of binocular rivalry.     

A fresh look at cancer metabolism in a historical setting

The Institute for Research in Biomedicine (IRB) Barcelona meeting on Cancer Metabolism took place in November 2010. It was organized with the support of the Banco Bilbao Vizcaya Argentaria Foundation and offered an outstanding line-up of acclaimed speakers within an intimate setting that allowed plenty of opportunity for informal interactions.     

A novel cohabitation between two diazotrophic cyanobacteria in the oligotrophic ocean

The cyanobacterial genus Trichodesmium is biogeochemically significant because of its dual role in nitrogen and carbon fixation in the oligotrophic ocean. Trichodesmium species form colonies that can be easily enriched from the water column and used for shipboard rate measurements to estimate their contribution to oceanic carbon and nitrogen budgets. During a July 2010 cruise near the Hawaiian Islands in the oligotrophic North Pacific Subtropical Gyre, a specific morphology of Trichodesmium puff-form colonies were examined under epifluorescent microscopy and found to harbor a colonial endobiont, morphologically identified as the heterocystous diazotrophic cyanobacterium Calothrix. Using unialgal enrichments obtained from this cruise, we show that these Calothrix-like heterocystous cyanobionts (hetDA for ‘Trichodesmium-associated heterocystous diazotroph'') fix nitrogen on a diurnal cycle (maximally in the middle of the light cycle with a detectable minimum in the dark). Gene sequencing of nifH from the enrichments revealed that this genus was likely not quantified using currently described quantitative PCR (qPCR) primers. Guided by the sequence from the isolate, new hetDA-specific primers were designed and subsequent qPCR of environmental samples detected this diazotroph from surface water to a depth of 150 m, reaching densities up to ∼9 × 10³ l⁻¹. Based on phylogenetic relatedness of nifH and 16S rRNA gene sequences, it is predicted that the distribution of this cyanobiont is not limited to subtropical North Pacific but likely reaches to the South Pacific and Atlantic Oceans. Therefore, this previously unrecognized cohabitation, if it reaches beyond the oligotrophic North Pacific, could potentially influence Trichodesmium-derived nitrogen fixation budgets in the world ocean.     

A fresh look at the fossil evidence for early Archaean cellular life

The rock record provides us with unique evidence for testing models as to when and where cellular life first appeared on Earth. Its study, however, requires caution. The biogenicity of stromatolites and 'microfossils' older than 3.0 Gyr should not be accepted without critical analysis of morphospace and context, using multiple modern techniques, plus rejection of alternative non-biological (null) hypotheses. The previous view that the co-occurrence of biology-like morphology and carbonaceous chemistry in ancient, microfossil-like objects is a presumptive indicator of biogenicity is not enough. As with the famous Martian microfossils, we need to ask not 'what do these structures remind us of?', but 'what are these structures?' Earth's oldest putative 'microfossil' assemblages within 3.4-3.5 Gyr carbonaceous cherts, such as the Apex Chert, are likewise self-organizing structures that do not pass tests for biogenicity. There is a preservational paradox in the fossil record prior to ca 2.7 Gyr: suitable rocks (e.g. isotopically light carbonaceous cherts) are widely present, but signals of life are enigmatic and hard to decipher. One new approach includes detailed mapping of well-preserved sandstone grains in the ca 3.4 Gyr Strelley Pool Chert. These can contain endolithic microtubes showing syngenicity, grain selectivity and several levels of geochemical processing. Preliminary studies invite comparison with a class of ambient inclusion trails of putative microbial origin and with the activities of modern anaerobic proteobacteria and volcanic glass euendoliths.     

A fresh look at the wolf-pack theory of companion-animal dog social behavior

A popular perspective on the social behavior of dogs in multiple-dog households sees the dogs' behavior as reflecting the sociobiological laws of the rigidly structured dominance hierarchy that has been described for wolf packs. This view suggests that aggression problems among dogs are natural expressions of conflict that arise whenever dominance status is in contention. One recommended solution has been for the owner to endorse and enforce a particular dominance hierarchy because, on the wolf pack model, aggression is minimized when the structure of the hierarchy is clear, strong, and stable. This article questions the validity of this perspective on 2 principal grounds. First, because it does not seem to occur in the wild, this article suggests the strong dominance hierarchy that has been described for wolves may be a by-product of captivity. If true, it implies that social behavior—even in wolves—may be a product more of environmental circumstances and contingencies than an instinctive directive. Second, because feral dogs do not exhibit the classic wolf-pack structure, the validity of the canid, social dominance hierarchy again comes into question. This article suggests that behavioral learning theory offers another perspective regarding the behavior of dogs and wolves in the wild or in captivity and offers an effective intervention for aggression problems.     

Potential contributions of vertically migrating Rhizosolenia to nutrient cycling and new production in the open ocean

We present a numerical model of nutrient uptake and photosynthesisduring migrations of the marine diatom Rhizosolenia that wasdeveloped to estimate fluxes of carbon and nitrogen due to thesemigrations in the open ocean. The predicted specific rate ofincrease of Rhizosolenia was 0.11–0.15 day¹, whereas thetotal time for one migration cycle ranged between 3 and 5 days.Using published estimates of Rhizosolenia abundance, we estimatethat new primary production due to Rhizosolenia migrations rangesbetween 0.018 and 0.033 mmol N m^–2 day^–1. Thesevalues represent up to 17% of new production due to turbulentdiffusive fluxes of nitrate into the euphotic zone and are ofthe same order of magnitude as new production due to nitrogenfixation in tropical oceans. Large-scale contributions of Rhizosoleniato oceanic new production are limited by their relatively lowstanding crop. Variations in the formulation of losses withdepth greatly affected gross and net fluxes of carbon and nitrogen.Better characterization of losses of Rhizosolenia and improvedestimates of its abundance will help determine more accuratelythe contributions of Rhizosolenia to global biogeochemical cycles. ¹Present address: Department of Agricultural and EnvironmentalScience, The Queen's University of Belfast New forge Lane, BelfastBT95PX, UK     

Bioturbation: a fresh look at Darwin's last idea

Bioturbation refers to the biological reworking of soils and sediments, and its importance for soil processes and geomorphology was first realised by Charles Darwin, who devoted his last scientific book to the subject. Here, we review some new insights into the evolutionary and ecological role of bioturbation that would have probably amazed Darwin. In modern ecological theory, bioturbation is now recognised as an archetypal example of 'ecosystem engineering', modifying geochemical gradients, redistributing food resources, viruses, bacteria, resting stages and eggs. From an evolutionary perspective, recent investigations provide evidence that bioturbation had a key role in the evolution of metazoan life at the end of the Precambrian Era.     

A fresh look at the origin of Plasmodium falciparum, the most malignant malaria agent

From which host did the most malignant human malaria come: birds, primates, or rodents? When did the transfer occur? Over the last half century, these have been some of the questions up for debate about the origin of Plasmodium falciparum, the most common and deadliest human malaria parasite, which is responsible for at least one million deaths every year. Recent findings bring elements in favor of a transfer from great apes, but are these evidences really solid? What are the grey areas that remain to be clarified? Here, we examine in depth these new elements and discuss how they modify our perception of the origin and evolution of P. falciparum. We also discuss the perspectives these new discoveries open.     

DMS dynamics in the most oligotrophic subtropical zones of the global ocean

The influences of physico-chemical and biological processes on dimethylsulfide (DMS) dynamics in the most oligotrophic subtropical zones of the global ocean were investigated. As metrics for the dynamics of DMS and the so-called ‘summer DMS paradox’ of elevated summer concentrations when surface chlorophyll a (Chl) and particulate organic carbon (POC) levels are lowest, we used the DMS-to-Chl and DMS-to-POC ratios in the context of three independent and complementary approaches. Firstly, field observations of environmental variables (such as the solar radiation dose, phosphorus limitation of phytoplankton and bacterial growth) were used alongside discrete DMS, Chl and POC estimates extracted from global climatologies (i.e., a ‘station based’ approach). We then used monthly climatological data for DMS, Chl, and POC averaged over the biogeographic province wherein a given oligotrophic subtropical zone resides (i.e., a ‘province based’ approach). Finally we employed sensitivity experiments with a new DMS module coupled to the ocean general circulation and biogeochemistry model PISCES to examine the influence of various processes in governing DMS dynamics in oligotrophic regions (i.e., a ‘model based’ approach). We find that the ‘station based’ and ‘province based’ approaches yield markedly different results. Interestingly, the ‘province based’ approach suggests the presence of a ‘summer DMS paradox’ in most all of the oligotrophic regions we studied. In contrast, the ‘station based’ approach suggests that the ‘summer DMS paradox’ is only present in the Sargasso Sea and eastern Mediterranean. Overall, we found the regional differences in the absolute and relative concentrations of DMS between 5 of the most oligotrophic regions of the world’s oceans were better accounted for by their nutrient dynamics (specifically phosphorus limitation) than by physical factors often invoked, e.g., the solar radiation dose. Our ‘model based’ experiments suggest that it is the limitation of phytoplankton/bacterial production and bacterial consumption of DMS by pervasive phosphorus limitation that is responsible for the ‘summer DMS paradox’.     

Growth and uptake kinetics of a facultatively oligotrophic bacterium at low nutrient concentrations

In oligotrophic waters, not only community structure but also physiological properties of heterotrophic bacteria are influenced by the concentration of organic matter.The relationship between growth rate of two facultatively oligotrophic strains ofAeromonas sp. No. 6 andFlavobacterium sp. M1 was studied in comparison with that of two eutrophic strains ofEscherichia coli 7020 andFlavobacterium sp. M2. These strains had two or three different substrate constants (Ks values) depending on substrate concentrations: Ks values for the two former were remarkably lower than those for the two latter. For instance, Ks value forAeromonas sp. No. 6 was about 8.9M when substrate concentration was greater than 53M and about 1.1M when substrate concentration was less man 53M. InE. coli the Ks value was about 260M at greater than 5600M and about 47M at less than 5600M substrate concentration.Uptake kinetics ofAeromonas sp. grown in a medium containing 2.7 mM glutamate (H-cell) and 0.11M glutamate (L-cell) have been determined for the intact cells. H-cell had two distinct values of Km for glutamate assimilation and respiration, and L-cell had three distinct values of Km for glutamate assimilation and respiration: In H-cell Km of assimilation was 2.8×10^–7 M and 1.5×10^–4 M, and Km of respiration was 2.3×10^–7 M and 1.7×10^–4 M; in L-cell Km of assimilation was 7.4×10^–8 M, 8.3×10^–6 M, and 1.3×10^–4 M, and Km of respiration was 2.5×10^–7, 8.9×10^–6M, and 1.7×10^–4 M. More than 60% of glutamate taken up by the H- and L-cells was respired when the substrate concentration was less than 10^–6 M, although at greater than 10^–6 M, 50% and 30% of glutamate was respired by H-cells and L-cells, respectively. These results suggest that the facultatively oligotrophic bacteria grow with high efficiency in environments with extremely low nutrient concentration, such as oligotrophic waters of lakes and ocean, as compared with in their growth in conditions of high nutrient concentraton, such as nutrient broth.     

Nutrient cycling in shallow,oligotrophic Lake Kvie,Denmark

The importance of isoetids for the exchange of dissolved inorganic nitrogen (DIN) between sediment and water was studied in shallow Lake Kvie, Denmark. Vegetated sediments from the littoral zone (55% of lake area) were compared to unvegetated sediments from the littoral and profundal zone. Clear effects of the isoetids were found on DIN in the porewater. At the vegetated station, NH₄ ⁺ showed the highest concentrations just below the surface (< 40 µM) whereas NO₃ ^- was dominating below 5 cm depth with concentrations up to 100 µM during the spring. The unvegetated littoral sediment showed a distinct change between winter where NH₄ ⁺ dominated and summer where NO₃ ^- was most abundant. NH₄ ⁺ dominated in the profundal sediment and showed increasing concentration with depth. The E_h was high (> 400 mV) in the vegetated sediment, indicating isoetid release of O₂ in the rhizosphere. A low DIN uptake was observed at the vegetated station while, based on porewater data, a diffusive release from the sediment was expected. This difference was due to plant assimilation. In general a release of NH₄ ⁺ and an uptake of NO₃ ^- was seen in all sediments. The denitrification rate calculated from the mass balance for the entire lake was 0.4 mmol m - 2 d^-1 and accounted for removal of 77% of the annual N-input to Lake Kvie.     

A comparative study on nutrient cycling in wet heathland ecosystems

Summary The term relative nutrient requirement is introduced in order to measure and to compare the nutrient losses from different perennial plant populations and the amount of nutrient that they need to absorb to compensate these losses. The relative nutrient requirement (L) is defined as the amount of the growth-limiting nutrient that must be taken up to maintain or replace each unit of biomass during a given time interval (e.g., mgN g^-1 biomass year^-1). It is derived that in a plant community with two competing perennial plant populations, species¹ will become dominant if the relative competition coefficient k ₁₂ (sensu De Wit 1960) exceeds the ratio between the relative nutrient requirements of the two species (L ₁/L ₂), whereas species 2 will become dominant, if k ₁₂ is below this critical ratio. The above-ground litter production was measured inwet heathland communities dominated by Erica tetralix or by Molinia caeruleain order to estimate N and P losses from theaboveground biomass and to calculate the relative N and P requirements of these species. Molinia lost during one year 63% and 34%, respectively, of the amount of N and P present in the above-ground biomass at the end of the growing season. These losses were in Erica 27% and 31%, respectively. The relative N requirements of the two species show the same difference: 7.5 and 2.6 mg N g^-1 yr^-1, respectively, in Molinia and in Erica. Also the relative P requirement of Molinia is higher as well as that of Erica (0.18 versus 0.08 mg P g^-1 yr^-1). The relative competition coefficient of Molinia with respect to Erica (k _me ) is equal to unity under unfertilized conditions but increases with increasing nutrient supply. Under nutrient-poor conditions k _me is below the critical ratio of the relative nutrient requirements of the two species (L _m /L _e =2.9 or 2.3), so that Erica will be the dominant species. After an increase in nutrient availability k _me increases and exceeds this critical limit which results in Molinia replacing Erica. During the last 20 years this replacement of Erica-dominant communities by monocultures of Molinia has been observed in almost all wet heathlands in The Netherlands along with a strong increase in nitrogen availability.     

A comparative study on nutrient cycling in wet heathland ecosystems

Summary The concept of the relative nutrient requirement (L _n) that was introduced in the first paper of this series is used to analyse the effects of the dominant plant population on nutrient cycling and nutrient mineralization in wet heathland ecosystems. A distinction is made between the effect that the dominant plant species has on (1) the distribution of nutrients over the plant biomass and the soil compartment of the ecosystem and (2) the recirculation rate of nutrients. The first effect of the dominant plant species can be calculated on the basis of the /k ratio (which is the ratio of the relative mortality to the decomposition constant). The second effect can be analysed using the relative nutrient requirement (L _n). The mass loss and the changes in the amounts of N and P in decomposing above-ground and below-ground litter produced by Erica tetralix and Molinia caerulea were measured over three years. The rates of mass loss from both above-ground and below-ground litter of Molinia were higher than those from Erica litter. After an initial leaching phase, litter showed either a net release or a net immobilization of nitrogen or phosphorus that depended on the initial concentrations of these nutrients. At the same sites, mineralization of nitrogen and phosphorus were measured for two years both in communities dominated by Molinia and in communities dominated by Erica. There were no clear differences in the nitrogen mineralization, but in one of the two years, phosphate mineralization in the Molinia-community was significantly higher. On the basis of the theory that was developed, mineralization rates and ratios between amounts of nutrients in plant biomass and in the soil were calculated on the basis of parameters that were independently measured. There was a reasonable agreement between predicted and measured values in the Erica-communities. In the Molinia-communities there were large differences between calculated and measured values, which was explained by the observation that the soil organic matter in these ecosystems still predominantly consisted of Erica-remains.