Effects of an increase in summer precipitation on leaf, soil, and ecosystem fluxes of CO2 and H2O in a sotol grassland in Big Bend National Park, Texas

Global climate models predict that in the next century precipitation in desert regions of the USA will increase, which is anticipated to affect biosphere/atmosphere exchanges of both CO₂ and H₂O. In a sotol grassland ecosystem in the Chihuahuan Desert at Big Bend National Park, we measured the response of leaf-level fluxes of CO₂ and H₂O 1 day before and up to 7 days after three supplemental precipitation pulses in the summer (June, July, and August 2004). In addition, the responses of leaf, soil, and ecosystem fluxes of CO₂ and H₂O to these precipitation pulses were also evaluated in September, 1 month after the final seasonal supplemental watering event. We found that plant carbon fixation responded positively to supplemental precipitation throughout the summer. Both shrubs and grasses in watered plots had increased rates of photosynthesis following pulses in June and July. In September, only grasses in watered plots had higher rates of photosynthesis than plants in the control plots. Soil respiration decreased in supplementally watered plots at the end of the summer. Due to these increased rates of photosynthesis in grasses and decreased rates of daytime soil respiration, watered ecosystems were a sink for carbon in September, assimilating on average 31 mmol CO₂ m⁻² s⁻¹ ground area day⁻¹. As a result of a 25% increase in summer precipitation, watered plots fixed eightfold more CO₂ during a 24-h period than control plots. In June and July, there were greater rates of transpiration for both grasses and shrubs in the watered plots. In September, similar rates of transpiration and soil water evaporation led to no observed treatment differences in ecosystem evapotranspiration, even though grasses transpired significantly more than shrubs. In summary, greater amounts of summer precipitation may lead to short-term increased carbon uptake by this sotol grassland ecosystem.     

Unique butyric acid incorporation patterns for salinosporamides A and B reveal distinct biosynthetic origins

Feeding sodium butyrate (0.25–1 mg/ml) to cultures of Salinispora tropica NPS21184 enhanced the production of salinosporamide B (NPI-0047) by 319% while inhibiting the production of salinosporamide A (NPI-0052) by 26%. Liquid chromatography mass spectrometry analysis of the crude extract from the strain NPS21184 fed with 0.5 mg/ml sodium [U-¹³C₄]butyrate indicated that butyrate was incorporated as a contiguous four-carbon unit into NPI-0047 but not into NPI-0052. Nuclear magnetic resonance analysis of NPI-0047 and NPI-0052 purified from the sodium [U-¹³C₄]butyrate-supplemented culture extract confirmed this incorporation pattern. The above finding is the first direct evidence to demonstrate that the biosynthesis of NPI-0047 is different from NPI-0052, and NPI-0047 is not a precursor of NPI-0052.     

Movements of undersized spotted grunter (<Emphasis Type="Italic">Pomadasys commersonnii</Emphasis>) in the Great Fish Estuary,South Africa: implications for fisheries management

The purpose of this study was to test the hypothesis that an estuarine species as the spotted grunter Pomadasys commersonnii is evenly distributed within the estuary and uniformly exploited by different groups of fishers. This was done by investigating the movements and area use of spotted grunter in relation to the fisheries. The position of 20 acoustically tagged fish was recorded during 36 days in February and March 2003, by manual tracking and automated data logging receivers. Information on the fisheries in the estuary was collected through visual registration of fishing effort and interviews. The spotted grunter moved on average 1.0 km (SD ± 0.7) between positional fixes. Most of the fish were positioned in the lower part of the 12 km long estuary, as 70% of the positional fixes were within the first 3 km, and 89% within the first 6 km. Approximately half (49%) of all the fixes were between 1.0 and 1.5 km from the estuary mouth. The spotted grunter used on average 4.9 km (SD ± 4.9) of the length of the estuary, and there was no significant relationship between the length of the estuary used and the body length of the fish (26–39 cm TL). Subsistence fishers accounted for 73% of fishing lines in the water, while recreational fishers accounted for the rest. Ninety-three percent of the lines were recorded within the first 6 km from the estuary mouth, of which 80% were recorded within the first 3 km. Almost 1/3 of the fishing effort was recorded between 1.0 and 1.5 km from the mouth. The hypothesis that the estuarine dependent species spotted grunter was evenly distributed within the estuary was rejected. However, there was a significant relationship between the distribution of the fishing effort of the subsistence fishers and the fish, indicating that the spotted grunter was uniformly exploited within the estuary by this group of fishers. In contrast, there was no relationship between the distribution of fish and recreational anglers.     

A 3-D model of coronary vessel development

Coronary vascular disease is one of the leading causes of mortality and morbidity in the United States. Therefore, a mechanistic understanding of coronary vessel morphogenesis would aid in the innovation of new therapies targeting vascular disorders. Moreover, a functionally equivalent in vitro model system allows for the delineation of the molecular mechanisms that regulate coronary vessel development. In this study, we present a novel in vitro model system. This three-dimensional (3-D) model system consists of a tubular scaffold, which is engineered from type-I collagen and has been optimized to support the growth of embryonic cardiac tissues. In this report, proepicardial (PE) cells, the developmental precursors of coronary vessels, have been isolated from several model species and cultured on this scaffold. In this model system, the PE cells were able to recapitulate several aspects of coronary vessel morphogenesis including epicardial formation, the epicardial to mesenchymal transformation, and de novo coronary vessel development or vasculogenesis. The differentiation of PE cells was characterized using a variety of specific protein markers. The potential uses of this novel coronary developmental model are discussed.     

Gene transfer to pre-hematopoietic and committed hematopoietic precursors in the early mouse Yolk Sac: a comparative study between <Emphasis Type="Italic">in situ</Emphasis> electroporation and retroviral transduction

Background  

Hematopoietic development in vertebrate embryos results from the sequential contribution of two pools of precursors independently generated. While intra-embryonic precursors harbour the features of hematopoietic stem cells (HSC), precursors formed earlier in the yolk sac (YS) display limited differentiation and self-renewal potentials. The mechanisms leading to the generation of the precursors in both sites are still largely unknown, as are the molecular basis underlying their different potential. A possible approach to assess the role of candidate genes is to transfer or modulate their expression/activity in both sites. We thus designed and compared transduction protocols to target either native extra-embryonic precursors, or hematopoietic precursors.     

Comprehensive analysis of proteins secreted by Trichophyton rubrum and Trichophyton violaceum under in vitro conditions

Dermatophytes cause most superficial mycoses in humans and animals. Their pathogenicity is probably linked with the secretion of proteins degrading keratinised structures. Using 2D-PAGE and a shotgun mass spectrometry approach, we identified 80 proteins from Trichophyton rubrum and Trichophyton violaceum secretomes, under conditions mimicking those in the host. Identified proteins included endo- and exoproteases, other hydrolases, and oxidoreductases. Our findings can contribute to a better understanding of the virulence mechanisms of the two species and the different types of infection they cause.     

Links between behaviour and metabolic physiology in fishes in the Anthropocene

Reviews in Fish Biology and Fisheries - Changes in behaviour and physiology are the primary responses of fishes to anthropogenic impacts such as climate change and over-fishing. Behavioural changes...     

Serial infection of diverse host (Mus) genotypes rapidly impedes pathogen fitness and virulence

Reduced genetic variation among hosts may favour the emergence of virulent infectious diseases by enhancing pathogen replication and its associated virulence due to adaptation to a limited set of host genotypes. Here, we test this hypothesis using experimental evolution of a mouse-specific retroviral pathogen, Friend virus (FV) complex. We demonstrate rapid fitness (i.e. viral titre) and virulence increases when FV complex serially infects a series of inbred mice representing the same genotype, but not when infecting a diverse array of inbred mouse strains modelling the diversity in natural host populations. Additionally, a single infection of a different host genotype was sufficient to constrain the emergence of a high fitness/high virulence FV complex phenotype in these experiments. The potent inhibition of viral fitness and virulence was associated with an observed loss of the defective retroviral genome (spleen focus-forming virus), whose presence exacerbates infection and drives disease in susceptible mice. Results from our experiments provide an important first step in understanding how genetic variation among vertebrate hosts influences pathogen evolution and suggests that serial exposure to different genotypes within a single host species may act as a constraint on pathogen adaptation that prohibits the emergence of more virulent infections. From a practical perspective, these results have implications for low-diversity host populations such as endangered species and domestic animals.     

A restatement of recent advances in the natural science evidence base concerning neonicotinoid insecticides and insect pollinators

A summary is provided of recent advances in the natural science evidence base concerning the effects of neonicotinoid insecticides on insect pollinators in a format (a ‘restatement'') intended to be accessible to informed but not expert policymakers and stakeholders. Important new studies have been published since our recent review of this field (Godfray et al. 2014 Proc. R. Soc. B 281, 20140558. (doi:10.1098/rspb.2014.0558)) and the subject continues to be an area of very active research and high policy relevance.