Masting is uncommon in trees that depend on mutualist dispersers in the context of global climate and fertility gradients

The benefits of masting (volatile, quasi-synchronous seed production at lagged intervals) include satiation of seed predators, but these benefits come with a cost to mutualist pollen and seed dispersers. If the evolution of masting represents a balance between these benefits and costs, we expect mast avoidance in species that are heavily reliant on mutualist dispersers. These effects play out in the context of variable climate and site fertility among species that vary widely in nutrient demand. Meta-analyses of published data have focused on variation at the population scale, thus omitting periodicity within trees and synchronicity between trees. From raw data on 12 million tree-years worldwide, we quantified three components of masting that have not previously been analysed together: (i) volatility, defined as the frequency-weighted year-to-year variation; (ii) periodicity, representing the lag between high-seed years; and (iii) synchronicity, indicating the tree-to-tree correlation. Results show that mast avoidance (low volatility and low synchronicity) by species dependent on mutualist dispersers explains more variation than any other effect. Nutrient-demanding species have low volatility, and species that are most common on nutrient-rich and warm/wet sites exhibit short periods. The prevalence of masting in cold/dry sites coincides with climatic conditions where dependence on vertebrate dispersers is less common than in the wet tropics. Mutualist dispersers neutralize the benefits of masting for predator satiation, further balancing the effects of climate, site fertility and nutrient demands.

Streptococcus agalactiae virulence factors isolated from bovine mastitis and antibiotic treatment response

AIMS

This study aims to characterise the virulence factors of S. agalactiae strains isolated from bovine mastitis and their potential association with the antibiotic treatment response.

METHODS AND RESULTS

Four different profiles were identified among the 181 S. agalactiae strains using polymerase chain reaction, of which hyl B and cylE were found in 100% of the isolated strains, followed by cfb (99.5%), scpB (40.3%), and lmb (15.5%). The cell invasion assay showed that lmb-positive strains exhibited higher invasion ability than lmb-negative. There was a significant association (P = 0.018) between lmb gene and cows that required more than one treatment cycle.

CONCLUSIONS

These results showed that intramammary infections caused by lmb-carrier S. agalactiae strains did not adequately respond to the antibiotics administered, likely because of the presence of this virulence factor, which potentially favours the cell invasion capacity of these strains.

Should we reconsider how to assess eutrophication?

Eutrophication in marine waters is traditionally assessed by checking if nutrients, algal biomass and oxygen are below/above a given threshold. However, increased biomass, nutrient concentrations and oxygen demand do not lead to undesirable environmental effects if the flow of carbon/energy from primary producers toward high trophic levels is consistently preserved. Consequently, traditional indicators might provide a misleading assessment of the eutrophication risk. To avoid this, we propose to evaluate eutrophication by using a new index based on plankton trophic fluxes instead of biogeochemical concentrations. A preliminary, model-based, assessment suggests that this approach might give a substantially different picture of the eutrophication status of our seas, with potential consequences on marine ecosystem management. Given the difficulties to measure trophic fluxes in the field, the use of numerical simulations is recommended although the uncertainty associated with biogeochemical models inevitably affects the reliability of the index. However, given the effort currently in place to develop refined numerical tools describing the marine environment (Ocean Digital Twins), a reliable, model-based, eutrophication index could be operational in the near future.

Limits to reproduction and seed size-number trade-offs that shape forest dominance and future recovery

The relationships that control seed production in trees are fundamental to understanding the evolution of forest species and their capacity to recover from increasing losses to drought, fire, and harvest. A synthesis of fecundity data from 714 species worldwide allowed us to examine hypotheses that are central to quantifying reproduction, a foundation for assessing fitness in forest trees. Four major findings emerged. First, seed production is not constrained by a strict trade-off between seed size and numbers. Instead, seed numbers vary over ten orders of magnitude, with species that invest in large seeds producing more seeds than expected from the 1:1 trade-off. Second, gymnosperms have lower seed production than angiosperms, potentially due to their extra investments in protective woody cones. Third, nutrient-demanding species, indicated by high foliar phosphorus concentrations, have low seed production. Finally, sensitivity of individual species to soil fertility varies widely, limiting the response of community seed production to fertility gradients. In combination, these findings can inform models of forest response that need to incorporate reproductive potential.

Globally, tree fecundity exceeds productivity gradients

Lack of tree fecundity data across climatic gradients precludes the analysis of how seed supply contributes to global variation in forest regeneration and biotic interactions responsible for biodiversity. A global synthesis of raw seedproduction data shows a 250-fold increase in seed abundance from cold-dry to warm-wet climates, driven primarily by a 100-fold increase in seed production for a given tree size. The modest (threefold) increase in forest productivity across the same climate gradient cannot explain the magnitudes of these trends. The increase in seeds per tree can arise from adaptive evolution driven by intense species interactions or from the direct effects of a warm, moist climate on tree fecundity. Either way, the massive differences in seed supply ramify through food webs potentially explaining a disproportionate role for species interactions in the wet tropics.

Author Correction: Continent-wide tree fecundity driven by indirect climate effects

A Correction to this paper has been published: https://doi.org/10.1038/s41467-021-22025-2

Continent-wide tree fecundity driven by indirect climate effects

Indirect climate effects on tree fecundity that come through variation in size and growth (climate-condition interactions) are not currently part of models used to predict future forests. Trends in species abundances predicted from meta-analyses and species distribution models will be misleading if they depend on the conditions of individuals. Here we find from a synthesis of tree species in North America that climate-condition interactions dominate responses through two pathways, i) effects of growth that depend on climate, and ii) effects of climate that depend on tree size. Because tree fecundity first increases and then declines with size, climate change that stimulates growth promotes a shift of small trees to more fecund sizes, but the opposite can be true for large sizes. Change the depresses growth also affects fecundity. We find a biogeographic divide, with these interactions reducing fecundity in the West and increasing it in the East. Continental-scale responses of these forests are thus driven largely by indirect effects, recommending management for climate change that considers multiple demographic rates.

Multiple trauma management in mountain environments - a scoping review : Evidence based guidelines of the International Commission for Mountain Emergency Medicine (ICAR MedCom). Intended for physicians and other advanced life support personnel

Background

Multiple trauma in mountain environments may be associated with increased morbidity and mortality compared to urban environments.

Objective

To provide evidence based guidance to assist rescuers in multiple trauma management in mountain environments.

Eligibility criteria

All articles published on or before September 30th 2019, in all languages, were included. Articles were searched with predefined search terms.

Sources of evidence

PubMed, Cochrane Database of Systematic Reviews and hand searching of relevant studies from the reference list of included articles.

Charting methods

Evidence was searched according to clinically relevant topics and PICO questions.

Results

Two-hundred forty-seven articles met the inclusion criteria. Recommendations were developed and graded according to the evidence-grading system of the American College of Chest Physicians. The manuscript was initially written and discussed by the coauthors. Then it was presented to ICAR MedCom in draft and again in final form for discussion and internal peer review. Finally, in a face-to-face discussion within ICAR MedCom consensus was reached on October 11th 2019, at the ICAR fall meeting in Zakopane, Poland.

Conclusions

Multiple trauma management in mountain environments can be demanding. Safety of the rescuers and the victim has priority. A crABCDE approach, with haemorrhage control first, is central, followed by basic first aid, splinting, immobilisation, analgesia, and insulation. Time for on-site medical treatment must be balanced against the need for rapid transfer to a trauma centre and should be as short as possible. Reduced on-scene times may be achieved with helicopter rescue. Advanced diagnostics (e.g. ultrasound) may be used and treatment continued during transport.

Identifying distribution and accumulation patterns of floating marine debris in the Black Sea

The distribution and accumulation of floating marine debris in the Black Sea during the last few decades are analysed by the help of numerical modelling. An approach based on a mesoscale circulation model combined with a particle tracking model is applied. It is established that the litter distribution is nearly independent of the source location and is mainly controlled by the basin circulation system. The western gyre predominantly accumulates floating debris in summer. After the integration of the main cyclonic current in winter, the debris in the inner basin moves east. Retention zones along the south-western coast persist in time. The mean particle stranding time is estimated at about 200 days. Accumulation zones along the south-eastern and eastern coast are abundant in summer, and then move further northeast and north. Simulations demonstrate an increasing litter accumulation in summer on the North Western Shelf and shelf break.

Surface water circulation develops seasonally changing patterns of floating litter accumulation in the Mediterranean Sea. A modelling approach

Marine litter and, particularly, plastics are a growing concern at global scale. The Mediterranean Sea is among the zones in the world with the highest concentration of floating plastic debris. However, our knowledge remains limited on the spatial distribution of litter across this basin. Here, a set of different numerical model simulations were conducted to examine the dynamic conditions of the surface layer of the Mediterranean and how this drives the circulation and accumulation of floating litter. Seasonal dynamics of surface water circulation led to contrasting distribution patterns of floating litter along the year. Multiple hot spots of litter zones appeared across the basin in summer, while litter disperses and moves towards the Eastern Mediterranean and nearshore waters in winter. Taking into account such seasonal variability in the spatial patterns of litter in the Mediterranean seems to be key in the design of further sampling surveys and management strategies.

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Surface current dynamics shows marked seasonality in the Mediterranean.

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Accumulation and distribution of floating particles follow currents patterns.

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Floating litter accumulates in diverse areas during different seasons.

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Lagrangian model helps to identify beaches impacted by floating litter.

Erratum to: 36th International Symposium on Intensive Care and Emergency Medicine: Brussels, Belgium. 15-18 March 2016

[This corrects the article DOI: 10.1186/s13054-016-1208-6.].

Choosing sheep (Ovis aries) as animal model for temporomandibular joint research: Morphological, histological and biomechanical characterization of the joint disc

Preclinical trials are essential to the development of scientific technologies. Remarkable molecular and cellular research has been done using small animal models. However, significant differences exist regarding the articular behavior between these models and humans. Thus, large animal models may be more appropriate to perform trials involving the temporomandibular joint (TMJ). The aim of this work was to make a morphological (anatomic dissection and white light 3D scanning system), histological (TMJ in bloc was removed for histologic analysis) and biomechanical characterization (tension and compression tests) of sheep TMJ comparing the obtained results with human data. Results showed that sheep processus condylaris and fossa mandibularis are anatomically similar to the same human structures. TMJ disc has an elliptical perimeter, thinner in the center than in periphery. Peripheral area acts as a ring structure supporting the central zone. The disc cells display both fibroblast and chondrocyte-like morphology. Marginal area is formed by loose connective tissue, with some chondrocyte-like cells and collagen fibers in diverse orientations. Discs obtained a tensile modulus of 3.97±0.73MPa and 9.39±1.67MPa, for anteroposterior and mediolateral assessment. The TMJ discs presented a compressive modulus (E) of 446.41±5.16MPa and their maximum stress value (σmax) was 18.87±1.33MPa. Obtained results suggest that these animals should be considered as a prime model for TMJ research and procedural training. Further investigations in the field of oromaxillofacial surgery involving TMJ should consider sheep as a good animal model due to its resemblance of the same joint in humans.

Evaluation of the efficacy of intramuscular versus intramammary treatment of subclinical Streptococcus agalactiae mastitis in dairy cows in Colombia

A randomized controlled trial was performed in 17 Colombian dairy herds to determine the cure risk among cows subclinically infected with Streptococcus agalactiae exposed to 2 antibiotic therapies. Composite milk samples were collected before milking at the onset of the trial (pretreatment) and 2 subsequent times over a period of approximately 63 d. The intramammary application (IMM) of ampicillin-cloxacillin was compared with the intramuscular application (IM) of penethamate hydriodide, and cure risks after an initial and retreatment application were assessed. Cure risk after the initial treatment was higher (82.4%) for the IMM treatment than for IM therapy (65.8%). However, no difference was observed in the cure risk of refractory cases after retreatment (IMM=52.6% vs. IM=51.2%). The cumulative cure risk (both initial and retreatment) was 90.4 and 82.9% for the IMM and IM products, respectively. A 2-level random effects logistic model that controlled for pretreatment cow-level somatic cell count, indicated that IM treatment (odds ratio=0.37) had a lower cure risk than IMM and a tendency for a lower cure risk with increasing baseline somatic cell count. Our findings suggest that both products and administration routes can reduce the prevalence of S. agalactiae in affected herds, but the IMM product had a better efficacy in curing the infection. In addition to the treatment protocol, the cow somatic cell count should be considered when making management decisions for cows infected with S. agalactiae.

Direct ageing of Thunnus thynnus from the eastern Atlantic Ocean and western Mediterranean Sea using dorsal fin spines

This study deals with important methodology issues that affect age estimates of eastern Atlantic bluefin tuna Thunnus thynnus using dorsal fin spines. Nearly 3800 spine sections were used from fish caught in the north-east Atlantic Ocean and western Mediterranean Sea over a 21 year period. Edge type and marginal increment analyses indicated a yearly periodicity of annulus formation with the translucent bands (50% of occurrence) appearing from October to May. Nucleus vascularization seriously affected specimens older than 6 years, with the disappearance of 40-50% of the presumed annuli by that age. An alternate sectioning location was a clear improvement and this finding is an important contribution to the methodology of using this structure for ageing the full-length range of eastern T. thynnus. Finally, there were no significant differences between the coefficients of von Bertalanffy growth model estimated from mean length at age data (L∞  = 327.4; k = 0.097; t0  = -0.838) and those estimated from the growth curves accepted for the eastern and western T. thynnus management units.

Understanding near/far-field engineering of optical dimer antennas through geometry modification

Numerical investigations based on the boundary element method (BEM) have been carried out to two-dimensional (2-D) silver dimer nano-antennas of various geometries. The near-field and far-field properties are mainly determined by the local geometry at the gap and the global shape of the antenna shafts respectively. A hybrid dimer antenna, which mixes the geometry ingredients of the rod dimer and the bowtie, benefits in both near and far field. Using a microcavity representation, the resonance in dimer nano-antennas is explained in a common and semi-analytical manner. The plasmonic enhancement and the wavelength mismatching in the optical dimer antenna are naturally embodied in this model. The quality factor of the resonance, which can be influenced by the wavelength and the geometry, is discussed intuitively. The understanding presented in this work could guide the future engineering of the optical dimer antenna.

Predictive factors in advanced head and neck cancer treated by radio-chemotherapy and hypoxia modification

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Background: Anemia and tumor hypoxia are known factors for resistance to radio-chemotherapy (RT-CT). In a previous report we have suggested that spinal cord stimulation (SCS) can modify tumor oxygenation and regional blood flow in head and neck cancer (HNC). The aim of the present prospective study was to test the predictive value of pO2 measurement in HNC treated by RT-CT and hypoxia modification using SCS. Methods: Twelve male patients with advanced HNC were analyzed. Stage IVb-IVa: 8–4; mean age 58 + 7.6 years (46–70). Scheduled therapy was hyperfractionated RT (120 cGy/fraction, two fractions/day, total dose 81.6 Gy) from a Co- 60 source, and tegafur 800 mg/day. SCS devices were placed before RT-CT under local anesthesia. During treatment, SCS was connected from 20–30 min before to 20–30 min after each radiotherapy session. Before treatment, they were assessed: Hemoglobin levels and tumor oxygenation pre-SCS and pos-SCS (measured by a polarographic probe system ‘pO2 Histograph‘), expressed as median-pO2, and the fraction of pO2 values less than 5 mmHg (HF5) and less than 2.5 mmHg (HF2.5). Correlations were assessed using Pearson and Spearman tests, and actuarial survival using Kaplan-Meier estimates and Log-rank test. Results: Hemoglobin levels were correlated with oxygenation pre-SCS and pos-SCS: median-pO2 (p=0.005 and p=0.011), HF5 (p=0.048 and p=0.005) respectively. Anemia was associated with more advanced stage (IVb vs IVa, p=0.022), higher HF5 pos-SCS (p=0.028) and lower disease-free survival (p=0.019). The HF2.5 pos-SCS was adversely correlated with the 2 years actuarial: disease-free survival (p=0.027), cause-specific survival (p=0.008) and overall survival (p=0.008). HF2.5 was also correlated with hematocrit (p=0.044). Conclusions: Low hemoglobin levels and anemia are associated with more hypoxic and more advanced tumors. Pre-treatment tumor hypoxia (assessed by the fraction of pO2 values less than 2.5 mmHg during-SCS) is a strong predictive factor for survival in advanced HNC. Patients with highly hypoxic tumors should be selected for more aggressive treatments. Partially supported by: Grant ‘FUNCIS: PI 31–98‘. Scientific supervision was carried out by GICOR.

No significant financial relationships to disclose.

Analysis of the molecular cascade responsible for mesodermal limb chondrogenesis: Sox genes and BMP signaling

Here, we have studied how Sox genes and BMP signaling are functionally coupled during limb chondrogenesis. Using the experimental model of TGFbeta1-induced interdigital digits, we dissect the sequence of morphological and molecular events during in vivo chondrogenesis. Our results show that Sox8 and Sox9 are the most precocious markers of limb cartilage, and their induction is independent and precedes the activation of BMP signaling. Sox10 appears also to cooperate with Sox9 and Sox8 in the establishment of the digit cartilages. In addition, we show that experimental induction of Sox gene expression in the interdigital mesoderm is accompanied by loss of the apoptotic response to exogenous BMPs. L-Sox5 and Sox6 are respectively induced coincident and after the expression of Bmpr1b in the prechondrogenic aggregate, and their activation correlates with the induction of Type II Collagen and Aggrecan genes in the differentiating cartilages. The expression of Bmpr1b precedes the appearance of morphological changes in the prechondrogenic aggregate and establishes a landmark from which the maintenance of the expression of all Sox genes and the progress of cartilage differentiation becomes dependent on BMPs. Moreover, we show that Ventroptin precedes Noggin in the modulation of BMP activity in the developing cartilages. In summary, our findings suggest that Sox8, Sox9, and Sox10 have a cooperative function conferring chondrogenic competence to limb mesoderm in response to BMP signals. In turn, BMPs in concert with Sox9, Sox6, and L-Sox5 would be responsible for the execution and maintenance of the cartilage differentiation program.

Comparative analysis of the expression and regulation of Wnt5a, Fz4, and Frzb1 during digit formation and in micromass cultures

Previous studies have shown that three members of the Wnt signaling pathway, the ligand WNT5A, the receptor FZ4, and the Wnt antagonist FRZB1, are implicated in the formation and differentiation of the digits. In this study, we have attempted to establish a functional correlation between them by comparing their expression patterns and their regulation by the signals controlling proliferation and differentiation of the limb mesoderm during formation of the avian digits in vivo and in micromass cultures. In vivo Wnt5a and Fz4 are expressed in the undifferentiated mesoderm of the autopod and in the differentiating digit cartilages. In the undifferentiated mesoderm, the expression of both genes is regulated positively by FGFs and negatively by bone morphogenetic proteins (BMPs). As chondrogenic differentiation starts, Fz4 becomes intensely up-regulated in the aggregate and in the developing perichondrium, whereas transcripts of Wnt5a are excluded from the core of the aggregate but maintained in the surrounding mesenchyme and perichondrium. In addition, at this stage, the expression of both genes become positively regulated by BMPs. These changes in expression and regulation are coincident with the induction of Frzb1 in the chondrogenic aggregate, which is expressed under the positive control of BMPs. Our findings fit with a role of Wnt5a/Fz4 negatively regulating in vivo the initiation and progression of cartilage differentiation. In vitro, only Frzb1 is expressed and regulated in a manner resembling that observed in vivo. Wnt5a and Fz4 are both expressed in the differentiating mesenchyme of micromass cultures, but their expression is not significantly regulated by the addition of FGF-2 or BMP-7 to the culture medium.

Is breath-hold time an objective index of exertional dyspnoea in humans?

Since dyspnoeic sensation (delta) increases progressively with work rate (WR) and the duration of a volitional breath-hold (tBH) shortens, we wished to explore whether tBH might correlate sufficiently closely with delta to provide a quantitative and descriptor-free index of respiratory sensation during dynamic exercise. Nine healthy males exercised on a cycle ergometer at a series of constant WRs, above and below the lactate threshold. Ventilatory and gas exchange variables were measured breath-by-breath. At each WR, breath-holds to the limit of tolerance were taken; delta was recorded (visual-analog scale) immediately prior to and throughout each breath-hold. During breath-holds, delta increased with time as a "break-away" monoexponential characteristic, reaching the maximum (100%) at the break-point. Despite end-tidal partial pressure of carbon dioxide at the break-point being higher and end-tidal partial pressure of oxygen being lower with increasing WR, the relationship between WR and tBH declined curvilinearly (i.e. with large falls in tBH occurring in the low WR range, but far smaller reductions at higher WRs). The tBH/minute ventilation relationship had a similar form. The relationship between pre-breath-hold delta and tBH was also complex: the large reductions in tBH in the low WR range were associated with only modest increases in pre-BH delta while, at higher WRs, the progressively smaller decrements in tBH were associated with progressively larger increases in delta. We therefore conclude that breath-hold duration is unlikely to provide a useful correlate of exertional dyspnoea during dynamic exercise. Furthermore, the relative prolongation of tBH at high WRs (accounting for the more-extreme levels of end-tidal gas tensions) may reflect the attention-diverting influence of the exercise per se.

Role of FGFs in the control of programmed cell death during limb development

We have investigated the role of FGFs in the control of programmed cell death during limb development by analyzing the effects of increasing and blocking FGF signaling in the avian limb bud. BMPs are currently considered as the signals responsible for cell death. Here we show that FGF signaling is also necessary for apoptosis and that the establishment of the areas of cell death is regulated by the convergence of FGF- and BMP-mediated signaling pathways. As previously demonstrated, cell death is inhibited for short intervals (12 hours) after administration of FGFs. However, this initial inhibition is followed (24 hours) by a dramatic increase in cell death, which can be abolished by treatments with a BMP antagonist (Noggin or Gremlin). Conversely, blockage of FGF signaling by applying a specific FGF-inhibitor (SU5402) into the interdigital regions inhibits both physiological cell death and that mediated by exogenous BMPs. Furthermore, FGF receptors 1, 2 and 3 are expressed in the autopodial mesoderm during the regression of the interdigital tissue, and the expression of FGFR3 in the interdigital regions is regulated by FGFs and BMPs in the same fashion as apopotosis. Together our findings indicate that, in the absence of FGF signaling BMPs are not sufficient to trigger apoptosis in the developing limb. Although we provide evidence for a positive influence of FGFs on BMP gene expression, the physiological implication of FGFs in apoptosis appears to result from their requirement for the expression of genes of the apoptotic cascade. We have identified MSX2 and Snail as candidate genes associated with apoptosis the expression of which requires the combined action of FGFs and BMPs.

Bone morphogenetic proteins regulate interdigital cell death in the avian embryo

The embryonic limb bud provides an excellent model for analyzing the mechanisms that regulate programmed cell death during development. At the time of digit formation in the developing autopod, the undifferentiated distal mesodermal cells may undergo or chondrogenic differentiation or apoptosis depending whether they are incorporated into the future digital rays or into the interdigital spaces. Both chondrogenesis or apoptosis are induced by local BMPS. However, whereas the chondrogenic-promoting activity of BMPs appears to be regulated through the BMPR-1b receptor, the mechanism by which the BMPs execute the death program remains unknown. The BMP proapoptotic activity requires the expression of members of the msx family of closely related homeobox-containing genes and is finally mediated by caspase activation, but the nature of the caspase(s) directly responsible for the cell death is also unknown. Finally, other growth factors present in the developing autopod at the stages of digit formation such as members of the FGF and TGF beta families modulate the ability of BMPs to induce cell death or chondrogenesis.

The BMP antagonist Gremlin regulates outgrowth, chondrogenesis and programmed cell death in the developing limb

In this study, we have analyzed the expression and function of Gremlin in the developing avian limb. Gremlin is a member of the DAN family of BMP antagonists highly conserved through evolution able to bind and block BMP2, BMP4 and BMP7. At early stages of development, gremlin is expressed in the dorsal and ventral mesoderm in a pattern complementary to that of bmp2, bmp4 and bmp7. The maintenance of gremlin expression at these stages is under the control of the AER, ZPA, and BMPs. Exogenous administration of recombinant Gremlin indicates that this protein is involved in the control of limb outgrowth. This function appears to be mediated by the neutralization of BMP function to maintain an active AER, to restrict the extension of the areas of programmed cell death and to confine chondrogenesis to the central core mesenchyme of the bud. At the stages of digit formation, gremlin is expressed in the proximal boundary of the interdigital mesoderm of the chick autopod. The anti-apoptotic influence of exogenous Gremlin, which results in the formation of soft tissue syndactyly in the chick, together with the expression of gremlin in the duck interdigital webs, indicates that Gremlin regulates the regression of the interdigital tissue. At later stages of limb development, gremlin is expressed in association with the differentiating skeletal pieces, muscles and the feather buds. The different expression of Gremlin in relation with other BMP antagonists present in the limb bud, such as Noggin, Chordin and Follistatin indicates that the functions of BMPs are regulated specifically by the different BMP antagonists, acting in a complementary fashion rather than being redundant signals.

Control of digit formation by activin signalling

Major advances in the genetics of vertebrate limb development have been obtained in recent years. However, the nature of the signals which trigger differentiation of the mesoderm to form the limb skeleton remains elusive. Previously, we have obtained evidence for a role of TGFbeta2 in digit formation. Here, we show that activins A and B and/or AB are also signals involved in digit skeletogenesis. activin betaA gene expression correlates with the initiation of digit chondrogenesis while activin betaB is expressed coincidently with the formation of the last phalanx of each digit. Exogenous administration of activins A, B or AB into the interdigital regions induces the formation of extra digits. follistatin, a natural antagonist of activins, is expressed, under the control of activin, peripherally to the digit chondrogenic aggregates marking the prospective tendinous blastemas. Exogenous application of follistatin blocks physiological and activin-induced digit formation. Evidence for a close interaction between activins and other signalling molecules, such as BMPs and FGFs, operating at the distal tip of the limb at these stages is also provided. Chondrogenesis by activins is mediated by BMPs through the regulation of the BMP receptor bmpR-1b and in turn activin expression is upregulated by BMP signalling. In addition, AER hyperactivity secondary to Wnt3A misexpression or local administration of FGFs, inhibits activin expression. In correlation with the restricted expression of activins in the course of digit formation, neither activin nor follistatin treatment affects the development of the skeletal components of the stylopod or zeugopod indicating that the formation of the limb skeleton is regulated by segment-specific chondrogenic signals.

Regulation by members of the transforming growth factor beta superfamily of the digital and interdigital fates of the autopodial limb mesoderm

Embryonic limb outgrowth is accomplished by the proliferation of mesodermal cells in the progress zone. In this region, mesodermal cells are maintained in an undifferentiated and proliferating state by the action of the apical ectodermal ridge (AER). Differentiation of these cells into individual skeletal elements occurs when the cells are displaced proximally and leave the influence of the AER as a consequence of the accumulation of cells in that region. Here we review the evidence obtained in the last few years showing that members of the transforming growth factor beta (TGFbeta) subfamily and bone morphogenetic proteins (BMPs) act as proximal signals in the autopod regulating the fate of the progress zone cells towards chondrogenesis or apoptosis. Our findings show that apoptosis is regulated by BMPs while chondrogenesis requires the interaction of TGFbetas and BMPs. Fibroblast growth factors (FGFs) produced by the AER exert an opposite function to both TGFbetas and BMPs, maintaining the progress zone cells in an undifferentiated state.

Expression and function of Gdf-5 during digit skeletogenesis in the embryonic chick leg bud

Bone morphogenetic proteins (BMPs) constitute a large family of secreted signals involved in the formation of the skeleton but the specific function of each member of this family remains elusive. GDF-5 is a member of the BMP family which has been implicated in several skeletogenic events including the induction and growth of the appendicular cartilages, the determination of joint forming regions, and the establishment of tendons. Here, we have studied the function of GDF-5 in digit skeletogenesis by analyzing the effects of its local administration in the developing autopod of embryonic chick and the regulation of its pattern of gene expression by other signals involved in digit morphogenesis. As reported in the mouse, the gdf-5 gene exhibits a precise distribution in the joint-forming regions of the developing chicken digital rays. GDF-5 beads implanted at the tip of the digits promote intense cartilage growth and fail to induce morphological or molecular signs of joint formation. Furthermore, GDF-5 beads implanted in the interdigits inhibit the formation of joints in the adjacent digits. These data suggest that the role of GDF-5 in joint formation is the control of growth and differentiation of the cartilage of the epiphyseal regions of the phalanges rather than accounting for the differentiation of the sinovial joint tissues. The interdigital mesoderm in spite of its potential to form ectopic digits with their tendinous apparatus failed to form either ectopic cartilages or ectopic tendons after the implantation of GDF-5 beads in the stages preceding cell death. At difference with other BMPs, GDF-5 exhibited only a weak cell death promoting effect. The BMP antagonist Noggin binds to GDF-5 and is able to inhibit all the observed effects of this growth factor in vivo. Potential interactions of GDF-5 with other signals involved in digits morphogenesis were also explored. BMP-7 regulates negatively the expression of gdf-5 gene in the joint forming regions and local treatment with Noggin induces the ectopic expression of gdf-5 in the interdigital mesoderm. Retroviral-induced misexpression of Indian or Sonic Hedgehog genes in the developing digits leads to the formation of digits without joints in which gdf-5 expression occurs throughout the entire perichondrial surface. In conclusion, this study indicates that GDF-5 is a signal regulated by other BMPs which controls the growth and differentiation of the epiphyses of the digital cartilages acting in close relationship with Hedgehog signaling.

A new approach to teaching prehospital trauma care to paramedic students

STUDY OBJECTIVE

A modification of the standard Department of Transportation student paramedic curriculum encouraging individualized patient assessment decreases inappropriate on-scene procedures (OSPs) and scene time, measured on simulated patients.

METHODS

Scenario-based testing from 1991 through 1993 was videotaped for all students. A new trauma curriculum was introduced in 1992, individualizing patient assessment and prioritization of OSPs. Recorded OSPs included spinal immobilization, application of military antishock trousers, endotracheal intubation, cricothyrotomy, intravenous catheter insertion, and needle thoracostomy. Twenty videotaped random student performances of the 1991 class was compared with a similar sample of 20 from the 1993 class; scene times and the OSP numbers were measured. Two board-certified independent emergency physicians unfamiliar with the students or the new curriculum reviewed all 40 tests on a master videotape. Patient assessment appropriateness, scene time, OSPs, scenario difficulty, and number of inappropriate OSPs were evaluated using a linear analog scale. Data are presented as means with confidence intervals (CIs), analyzed by Student's t test and the Mann-Whitney 2-sample test.

RESULTS

Scene time from 1991 to 1993 decreased overall with a mean of 4.3 minutes (95% CI 2.8 to 5.8 minutes), as did the number of OSPs: 3.1 versus 1.7 (mean difference, 1.45 OSPs per scenario; 95% CI.91 to 1.99). Physician reviewers noted improvements in the appropriateness of patient assessment, scene time, and OSPs from 1991 to 1993. There was no significant difference in scenario difficulty for 1991 compared with 1993. Inappropriate OSPs done on scene declined. Physician 1 indicated a mean of inappropriate procedures of 1.6 in 1991 versus.5 in 1993. Physician 2 indicated a mean of 1.4 in 1991 versus.3 in 1993.

CONCLUSION

This new paramedic curriculum decreased on-scene time and inappropriate use of procedures in stabilizing the condition of patients with simulated critical trauma.

Morphogenesis of digits in the avian limb is controlled by FGFs, TGFbetas, and noggin through BMP signaling

In the final stages of limb morphogenesis, autopodial cells leaving the progress zone differentiate into cartilage or undergo apoptotic cell death, depending on whether they are incorporated into the digital rays or interdigital spaces. Most evidence indicates that these two opposite fates of the autopodial mesoderm are controlled by BMP signaling. However, the molecular basis for these two distinct actions of BMPs, including the receptors involved in the process, is controversial. In this study we have addressed this question by exploring the presence in the developing autopod of diffusible signals able to modulate BMP function and by analyzing the effects of their exogenous administration on the pattern of expression of BMP receptor genes. Our findings show that tgfbeta2 and noggin genes are expressed in the condensing region of the developing digital rays in addition to the well-known distribution in the autopodial tissues of FGFs (apical ectodermal ridge, AER) and BMPs (AER, progress zone mesoderm, and interdigital regions). Exogenous administration of all the factors causes changes in the expression of the bmpR-1b gene which are followed by parallel alterations of the skeletal phenotype: FGFs inhibit the expression of bmpR-1b compatible with their function in the maintenance of the progress zone mesoderm in an undifferentiated state; and TGFbetas induce the expression of bmpR-1b and promote ectopic chondrogenesis, compatible with a function in the establishment of the position of the digital rays. In addition we provide evidence for the occurrence of an interactive loop between BMPs and noggin accounting for the spatial distribution of bmpR-1b which may control the size and shape of the skeletal pieces. In contrast to the bmpR-1b gene, the bmpR-1a gene is expressed at low levels in the autopodial mesoderm and its expression is not modified by any of the tested factors regardless of their effects on chondrogenesis or cell death. Finally, the role of BMPs in programmed cell death is confirmed here by the intense inhibitory effect of noggin on apoptosis, but the lack of correlation between changes in the pattern of cell death induced by treatment with the studied factors and the expression of either bmpR-1a or bmpR-1b genes suggest that a still-unidentified BMP receptor may account for this BMP function.

Morphological diversity of the avian foot is related with the pattern of msx gene expression in the developing autopod

The formation of the digits in amniota embryos is accompanied by apoptotic cell death of the interdigital mesoderm triggered through BMP signaling. Differences in the intensity of this apoptotic process account for the establishment of the different morphological types of feet observed in amniota (i.e., free-digits, webbed digits, lobulated digits). The molecular basis accounting for the differential pattern of interdigital cell death remains uncertain since the reduction of cell death in species with webbed digits is not accompanied by a parallel reduction in the pattern of expression of bmp genes in the interdigital regions. In this study we show that the duck interdigital web mesoderm exhibits an attenuated response to both BMP-induced apoptosis and TGFbeta-induced chondrogenesis in comparison with species with free digits. The attenuated response to these signals is accompanied by a reduced pattern of expression of msx-1 and msx-2 genes. Local application of FGF in the duck interdigit expands the domain of msx-2 expression but not the domain of msx-1 expression. This change in the expression of msx-2 is followed by a parallel increase in spontaneous and exogenous BMP-induced interdigital cell death, while the chondrogenic response to TGFbetas is unchanged. The regression of AER, as deduced by the pattern of extinction of fgf-8 expression, takes place in a similar fashion in the chick and duck regardless of the differences in interdigital cell death and msx gene expression. Implantation of BMP-beads in the distal limb mesoderm induces AER regression in both the chick and duck. This finding suggests an additional role for BMPs in the physiological regression of the AER. It is proposed that the formation of webbed vs free-digit feet in amniota results from a premature differentiation of the interdigital mesoderm into connective tissue caused by a reduced expression of msx genes in the developing autopod.

Program for reducing pedestrian-motor vehicle crashes

Injury prevention has been identified as a component of emergency medicine. However, involvement of emergency physicians in injury prevention has been hindered by clinical responsibilities, lack of financial support, and limited expertise in skills necessary for effective injury prevention programs. This article describes the development and content of a statewide pedestrian safety plan prepared by the Department of Emergency Medicine at the University of New Mexico. The plan included a written document, community input through focus groups, and a public information campaign. The written document included a synthesis of published literature, state-specific data, information on community interventions, and recommendations for state agencies and other groups interested in reducing pedestrian injuries. This project can be modeled at other academic EDs with an interest in injury prevention and pedestrian safety.

Role of BMP-2 and OP-1 (BMP-7) in programmed cell death and skeletogenesis during chick limb development

Bone Morphogenetic Protein 2 (BMP-2) and Osteogenic Protein 1 (OP-1, also termed BMP-7) are members of the transforming growth factor beta superfamily. In the present study, we have analyzed the effects of administering them locally at different stages and locations of the chick limb bud using heparin beads as carriers. Our results show that these BMPs are potent apoptotic signals for the undifferentiated limb mesoderm but not for the ectoderm or the differentiating chondrogenic cells. In addition, they promote intense radial growth of the differentiating cartilages and disturb the formation of joints accompanied by alterations in the pattern of Indian hedgehog and ck-erg expression. Interestingly, the effects of these two BMPs on joint formation were found to be different. While the predominant effect of BMP-2 is alteration in joint shape, OP-1 is a potent inhibitory factor for joint formation. In situ hybridizations to check whether this finding was indicative of specific roles for these BMPs in the formation of joints revealed a distinct and complementary pattern of expression of these genes during the formation of the skeleton of the digits. While Op-1 exhibited an intense expression in the perichondrium of the developing cartilages with characteristic interruptions in the zones of joint formation, Bmp-2 expression was a positive marker for the articular interspaces. These data suggest that, in addition to the proposed role for BMP-2 and OP-1 in the establishment of the anteroposterior axis of the limb, they may also play direct roles in limb morphogenesis: (i) in regulating the amount and spatial distribution of the undifferentiated prechondrogenic mesenchyme and (ii) in controlling the location of the joints and the diaphyses of the cartilaginous primordia of the long bones once the chondrogenic aggregates are established.

Role of TGF beta s and BMPs as signals controlling the position of the digits and the areas of interdigital cell death in the developing chick limb autopod

The establishment of the digital rays and the interdigital spaces in the developing limb autopod is accompanied by the occurrence of corresponding domains of expression of TGF beta s and BMPs. This study analyzes whether these coincident events are functionally correlated. The experiments consisted of local administration of TGF beta-1, TGF beta-2 or BMP-4 by means of heparin or Affi-gel blue beads to the chick limb autopod in the stages preceding the onset of interdigital cell death. When beads bearing either TGF beta-1 or −2 were implanted in the interdigits, the mesodermal cells were diverted from the death program forming ectopic cartilages or extra digits in a dose- and stage-dependent fashion. This change in the interdigital phenotype was preceded by a precocious ectopic expression of ck-erg gene around the bead accompanied by down-regulation of bmp-4, msx-1 and msx-2 gene expression. When BMP-beads were implanted in the interdigital spaces, programmed cell death and the freeing of the digits were both accelerated. Implantation of beads bearing BMP-4 at the tip of the growing digits was followed by digit bifurcation, accompanied by the formation of an ectopic area of cell death resembling an extra interdigit, both morphologically and molecularly. The death-inducing effect of the BMP beads and the chondrogenic-inducing effect of the TGF beta beads were antagonized by the implantation of an additional bead preabsorbed with FGF-2, which constitutes a signal characteristic of the progress zone. It is concluded that the spatial distribution of digital rays and interdigital spaces might be controlled by a patterned distribution of TGF beta s and BMPs in the mesoderm subjacent to the progress zone.

In vivo inhibition of programmed cell death by local administration of FGF-2 and FGF-4 in the interdigital areas of the embryonic chick leg bud

The formation of the digits in amniote vertebrates is accompanied by a massive degeneration process that accounts for the disappearance of the interdigital mesenchyme. The establishment of these areas of interdigital cell death (INZs) is concomitant with the flattening of the apical ectodermal ridge (AER), but a possible causal relationship between these processes has not been demonstrated. Recent studies have shown that the function of the AER can be substituted for by implantation of beads bearing either FGF-2 or FGF-4 into the apical mesoderm of the early limb bud. According to these observations, if the onset of INZs is triggered by the cessation of the AER function, local administration of FGFs to the interdigital tissue prior to cell death should delay or inhibit interdigit degeneration. In the present study we have confirmed this prediction. Implanting Affi-gel blue or heparin beads pre-absorbed with either FGF-2 or FGF-4 into the interdigital tissue of the chick leg bud in the stages prior to cell death stimulates cell proliferation and causes the formation of webbed digits. Vital staining with neutral red confirmed an intense temporal inhibition of interdigital cell death after FGF treatment. This inhibition of interdigital cell death was not accompanied by modifications in the pattern of expression of Msx-1 or Msx-2 genes, which in normal development display a domain of expression in the interdigital tissue preceding the onset of degeneration.

Shh, HoxD, Bmp-2, and Fgf-4 gene expression during development of the polydactylous talpid2, diplopodia1, and diplopodia4 mutant chick limb buds

Several polydactylous mutants affect the pattern of asymmetry along the anteroposterior axis of the vertebrate limb. In talpid2, diplopodia1, and diplopodia4 chick limb mutants, there is a preaxial extension that results in broader limb buds. Talpid2 shows reduction of the long bones and 9-10 syndactylous digits, none of which are specifically recognizable as members of the normal digit complement. In diplopodia1 and diplopodia4 extra digits are present preaxially in addition to the normal digits. This phenotype resembles the duplications obtained by grafting a polarizing region to the anterior margin of the limb bud. The abnormal skeletal pattern along the anteroposterior limb axis in both mutants suggests alterations in the signaling pathways that mediate growth and patterning of the limb. In situ hybridization studies reveal that whereas shh transcripts are restricted to the posterior limb margins, HoxD, Bmp-2, and Fgf-4 genes are ectopically expressed in the anterior region of the talpid2, diplopodia1, and diplopodia4 limb buds. The results obtained give insights into the molecular basis of talpid2 and diplopodia mutations and also into the possible roles of shh, Bmp-2, HoxD, and Fgf-4 genes in vertebrate limb morphogenesis.

Two cases of malignant lymphoma complicating autoimmune (Hashimoto's) thyroiditis

The occurrence of lymphoma of the thyroid in a setting of autoimmune thyroid disease is being recognized with increasing frequency. The usual presentation is a rapidly enlarging goiter. This article describes two cases of this condition and emphasizes how prompt diagnosis and treatment can yield satisfactory results.

Cell death in the embryonic developing limb

In amniote vertebrates, the development of form and structure of the limb bud is accompanied by precise patterns of massive mesodermal cell death with morphological features of apoptosis. These areas of cell death appear to eliminate undifferentiated cells which are required only for a limited time period of limb development. Predictable skeletal and morphological anomalies of the limb occur when the pattern of cell death is modified in mutant species or under experimental conditions. Most evidence points to the occurrence of local triggering mechanisms to account for the establishment of the areas of cell death and the subsequent activation of cell death genes. Modifications of the extracellular matrix and diminution in the contribution of growth factors by neighbouring tissues appear as the most likely potential candidates for triggering the cell death program. Information on the genetical basis of cell death in the developing limb is very scarce. Among the increasing number of cell death genes identified in other cell death systems, such as p-53 and the ced-3/ICE and ced-9/ bcl-2 gene families, only bcl-2 has been studied in detail during limb development and yet, the information obtained is contradictory. Bcl-2 is not expressed in the areas of cell death of the developing limb, but normal limbs develop in mice with disruption of the bcl-2 gene. Obviously, the clarification of the role of the cell death genes constitute a major task in future studies of cell death in the developing limb.

Formation of extra digits in the interdigital spaces of the chick leg bud is not preceded by changes in the expression of the Msx and Hoxd genes

By in situ hybridization we studied the expression patterns of Msx and Hoxd genes during the late development of the chick leg autopodium (foot) and compared them to patterns during the experimental development of interdigital extra digits. Extra digits are induced in the third interdigital space after various experimental manipulations, such as transient isolation of the interdigit, or removal of the interdigital marginal ectoderm and mesoderm. Msx1 and Msx2 are normally expressed in the interdigital tissue programmed to die. Our experiment changes the fate of the interdigital tissue from cell death to chondrogenesis and provides a good model for studying Msx involvement in defining areas of programmed cell death. Among the proposed roles of Hoxd genes is their involvement in the specification of digit identity early in development. The induction of extra digits allows us to examine whether this new morphogenetic commitment of the interdigital tissues involves changes in the domains of expression of Hoxd genes. Our results show that extra digits develop without a previous modification of the normal pattern of expression of Msx or Hoxd genes. This observation does not support the correlation between the expression of Msx genes and programmed cell death and suggests a role for these genes in maintaining the interdigital tissue in an undifferentiated state. Our results show that an increased number of digits can be formed without modifications in the pattern of expression of the 5'-located Hoxd genes and suggest the existence of latent or residual digit organization mechanisms past the time when digits are normally determined, independent of Hoxd gene expression.

Extracellular matrix arrangement in the papillary muscles of the adult rat heart. Alterations after doxorubicin administration and experimental hypertension

In the present study, we analyzed the components of the extracellular matrix (ECM) and its arrangement at the level of the papillary muscles in the adult rat heart using light and transmission and scanning electron microscopy techniques. Our results reveal that after a single dose (6 mg/kg) of dexorubicin to cause a significant decrease and disorganization of the endomysium and perimysium in the first week after injection, affecting the endomysial struts and perimysial strands. Degenerating myocytes and alterations of the coiled perimysial fibers were characteristic 4 weeks after treatment. After 8 weeks, ultrastructural alterations at the level of the plasma membrane of the myocytes and adjacent collagen network were present in the tip of the papillary muscles. These alterations may be responsible for the inefficiency of the valvular apparatus as an initial factor implicated in doxorubicin-induced congestive heart failure. Experimental hypertension, produced by constriction of the abdominal aorta, induced hypertrophy of the left ventricle, with increased perimysium and endomysium of the ECM at the level of the papillary muscles 4 weeks after aortic banding. Interstitial and perivascular fibrosis were observed 8 weeks after surgical treatment, and macrophages around the degenerating myocytes were characteristic 16 weeks after treatment. These alterations of the ECM network have been correlated with their possible implication in ventricular biomechanical properties.

Pattern regulation in the chick autopodium at advanced stages of embryonic development

In previous studies we have observed that the interdigital tissue of the chick embryo leg bud during the stages previous to interdigital cell death exhibits a considerable chondrogenic potentiality both in vivo and in vitro. In the present investigation we have carried out a variety of experimental manipulations of the chick leg bud at stage 29 to discover possible mechanisms accounting for interdigital ectopic chondrogenesis and extradigit formation. Our results show that the interdigital tissue is capable of forming an extradigit when temporarily isolated microsurgically and regrafted in its original location and after deletion of one of the adjacent digital primordia, suggesting that developing phalangeal cartilages exercise an inhibitory effect on chondrification in adjoining tissues. Furthermore, and of greater importance, ablation of the primordium of a digit is followed by normal development of the definitive digit if the wound surfaces are suitably apposed. These results reveal a considerable regulatory potential in the autopodium at advanced stages of development.

Internucleosomal DNA fragmentation and programmed cell death (apoptosis) in the interdigital tissue of the embryonic chick leg bud

In this work we have attempted to characterize the programmed cell death process in the chick embryonic interdigital tissue. Interdigital cell death is a prominent phenomenon during limb development and has the role of sculpturing the digits. Morphological changes in the regressing interdigital tissue studied by light, transmission and scanning electron microscopy were correlated with the occurrence of internucleosomal DNA fragmentation, evaluated using agarose gels. Programming of the cell death process was also analyzed by testing the chondrogenic potential of the interdigital mesenchyme, in high density cultures. Our results reveal a progressive loss of the chondrogenic potential of the interdigital mesenchyme, detectable 36 hours before the onset of the degenerative process. Internucleosomal DNA fragmentation was only detected concomitant with the appearance of cells dying with the morphology of apoptosis, but unspecific DNA fragmentation was also present at the same time. This unspecific DNA fragmentation was explained by a precocious activation of the phagocytic removal of the dying cells, confirmed in the tissue sections. From our observations it is suggested that programming of cell death involves changes before endonuclease activation. Further, cell surface changes involved in the phagocytic uptake of the dying cells appear to be as precocious as endonuclease activation.

Modification of the phalangeal pattern of the digits in the chick embryo leg bud by local microinjection of RA, staurosporin and TGF beta's

Many experimental studies show that in the avian chick limb the digits are specified at early stages of development by characteristic concentrations within the limb mesoderm of a still unidentified morphogen diffusing from the posterior margin of the bud, linked with a specific pattern of homeobox gene expression. In all these studies, digits are distinguished by their size, morphology and phalangeal pattern rather than by their position within the autopodium. In this work we report the induction of digits that have otherwise normal morphology but lack an interphalangeal joint. This suggests that the patterning of these joints is not necessarily linked to the control of the outgrowth of the digital rays. Missing interphalangeal joints were induced by microinjection into the third interdigital space of the leg bud of stage 28 to 31 chick embryos of retinoic Acid (RA), staurosporine and TGF beta 1 and beta 2, but not by microinjection of FGF or EGF. Our results also suggest that the pattern of insertion of the long tendons and the formation of the flexor cutaneous pad at the plantar surface of the digits are both linked to the establishment of the interphalangeal joints.

Clinically occult presentation of comminuted intertrochanteric hip fractures

Hip fractures in awake patients are rarely subtle in their clinical presentation. We report two cases of occult, comminuted, intertrochanteric hip fractures that occurred in awake, elderly patients who were brought to the emergency department for evaluation of other medical conditions. Neither patient complained of hip pain, and both were transported to the ED without spinal immobilization. Physical examination revealed no sign of hip fracture. Patient 1 was scheduled for admission and just prior to transfer out of the ED developed hip pain. Patient 2 was admitted for workup of possible transient ischemic attack and approximately 2.5 hours after admission complained of hip pain. Radiographs of both patients revealed comminuted intertrochanteric hip fractures. In an elderly, nonambulatory patient who may have fallen prior to evaluation, routine radiographs of the pelvis and hip should be performed followed by plain tomography, computed tomography, bone scan, or magnetic resonance imaging as indicated to rule out occult hip fracture. Even comminuted intertrochanteric hip fractures can present in an occult fashion; therefore, a high index of suspicion must be maintained for these injuries.