Evaluating Pigments as a Biosignature: Abiotic/Prebiotic Synthesis of Pigments and Pigment Mimics in Planetary Environments

Pigments serve a multitude of functions in biology including light harvesting for photosynthesis, radiation protection, membrane support, and defense. The ubiquity of pigments-especially within extremophiles found in high-radiation, high-salinity, and dry environments-and their detectability via mission-ready techniques have elevated these molecules as promising targets in the search for evidence of life elsewhere. Moreover, the detection of pigments has been proposed as a "smoking gun" for extraterrestrial life as it has been suggested that these molecules cannot be generated abiotically. However, while pigments may hold promise as a biosignature, current understanding of their possible prebiotic origins remains understudied and uncertain. Better understanding of the abiotic synthesis of pigments is critical for evaluating the biogenicity of any pigment detected during missions, including by the Mars Perseverance rover or from returned samples. Compounding this uncertainty is the broad definition of pigment as it includes any compound capable of absorbing visible light and by itself does not specify a particular chemical motif. While not experimentally verified, there are promising prebiotic routes for generating pigments including hemes, chlorophylls, and carotenoids. Herein, we review the biochemistry of pigments, the inherent assumptions made when searching for these molecules in the field, their abiotic synthesis in industry and prebiotic reactions, prebiotically relevant molecules that can mimic their spectral signatures, and implications/recommendations for future work.

Chapter 4: A Geological and Chemical Context for the Origins of Life on Early Earth

Within the first billion years of Earth's history, the planet transformed from a hot, barren, and inhospitable landscape to an environment conducive to the emergence and persistence of life. This chapter will review the state of knowledge concerning early Earth's (Hadean/Eoarchean) geochemical environment, including the origin and composition of the planet's moon, crust, oceans, atmosphere, and organic content. It will also discuss abiotic geochemical cycling of the CHONPS elements and how these species could have been converted to biologically relevant building blocks, polymers, and chemical networks. Proposed environments for abiogenesis events are also described and evaluated. An understanding of the geochemical processes under which life may have emerged can better inform our assessment of the habitability of other worlds, the potential complexity that abiotic chemistry can achieve (which has implications for putative biosignatures), and the possibility for biochemistries that are vastly different from those on Earth.

Chapter 1: The Astrobiology Primer 3.0

The Astrobiology Primer 3.0 (ABP3.0) is a concise introduction to the field of astrobiology for students and others who are new to the field of astrobiology. It provides an entry into the broader materials in this supplementary issue of Astrobiology and an overview of the investigations and driving hypotheses that make up this interdisciplinary field. The content of this chapter was adapted from the other 10 articles in this supplementary issue and thus represents the contribution of all the authors who worked on these introductory articles. The content of this chapter is not exhaustive and represents the topics that the authors found to be the most important and compelling in a dynamic and changing field.

Electron transport chains as a window into the earliest stages of evolution

The origin and early evolution of life is generally studied under two different paradigms: bottom up and top down. Prebiotic chemistry and early Earth geochemistry allow researchers to explore possible origin of life scenarios. But for these "bottom-up" approaches, even successful experiments only amount to a proof of principle. On the other hand, "top-down" research on early evolutionary history is able to provide a historical account about ancient organisms, but is unable to investigate stages that occurred during and just after the origin of life. Here, we consider ancient electron transport chains (ETCs) as a potential bridge between early evolutionary history and a protocellular stage that preceded it. Current phylogenetic evidence suggests that ancestors of several extant ETC components were present at least as late as the last universal common ancestor of life. In addition, recent experiments have shown that some aspects of modern ETCs can be replicated by minerals, protocells, or organic cofactors in the absence of biological proteins. Here, we discuss the diversity of ETCs and other forms of chemiosmotic energy conservation, describe current work on the early evolution of membrane bioenergetics, and advocate for several lines of research to enhance this understanding by pairing top-down and bottom-up approaches.

A Review on Hypothesized Metabolic Pathways on Europa and Enceladus: Space-Flight Detection Considerations

Enceladus and Europa, icy moons of Saturn and Jupiter, respectively, are believed to be habitable with liquid water oceans and therefore are of interest for future life detection missions and mission concepts. With the limited data from missions to these moons, many studies have sought to better constrain these conditions. With these constraints, researchers have, based on modeling and experimental studies, hypothesized a number of possible metabolisms that could exist on Europa and Enceladus if these worlds host life. The most often hypothesized metabolisms are methanogenesis for Enceladus and methane oxidation/sulfate reduction on Europa. Here, we outline, review, and compare the best estimated conditions of each moon's ocean. We then discuss the hypothetical metabolisms that have been suggested to be present on these moons, based on laboratory studies and Earth analogs. We also detail different detection methods that could be used to detect these hypothetical metabolic reactions and make recommendations for future research and considerations for future missions.

Determining the "Biosignature Threshold" for Life Detection on Biotic, Abiotic, or Prebiotic Worlds

The field of prebiotic chemistry has demonstrated that complex organic chemical systems that exhibit various life-like properties can be produced abiotically in the laboratory. Understanding these chemical systems is important for astrobiology and life detection since we do not know the extent to which prebiotic chemistry might exist or have existed on other worlds. Nor do we know what signatures are diagnostic of an extant or "failed" prebiotic system. On Earth, biology has suppressed most abiotic organic chemistry and overprints geologic records of prebiotic chemistry; therefore, it is difficult to validate whether chemical signatures from future planetary missions are remnant or extant prebiotic systems. The "biosignature threshold" between whether a chemical signature is more likely to be produced by abiotic versus biotic chemistry on a given world could vary significantly, depending on the particular environment, and could change over time, especially if life were to emerge and diversify on that world. To interpret organic signatures detected during a planetary mission, we advocate for (1) gaining a more complete understanding of prebiotic/abiotic chemical possibilities in diverse planetary environments and (2) involving experimental prebiotic samples as analogues when generating comparison libraries for "life-detection" mission instruments.

Planetary Minerals Catalyze Conversion of a Polycyclic Aromatic Hydrocarbon to a Prebiotic Quinone: Implications for Origins of Life

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous in astrochemical environments and are disbursed into planetary environments via meteorites and extraterrestrial infall where they may interact with mineral phases to produce quinones important for origins of life. In this study, we assessed the potential of the phyllosilicates montmorillonite (MONT) and kaolinite (KAO), and the enhanced Mojave Mars Simulant (MMS) to convert the PAH anthracene (ANTH) to the biologically important 9,10-anthraquinone (ANTHQ). All studied mineral substrates mediate conversion over the temperature range assessed (25-500°C). Apparent rate curves for conversion were sigmoidal for MONT and KAO, but quadratic for MMS. Conversion efficiency maxima for ANTHQ were 3.06% ± 0.42%, 1.15% ± 0.13%, and 0.56% ± 0.039% for MONT, KAO, and MMS, respectively. We hypothesized that differential substrate binding and compound loss account for the apparent conversion kinetics observed. Apparent loss rate curves for ANTH and ANTHQ were exponential for all substrates, suggesting a pathway for wide distribution of both compounds in warmer prebiotic environments. These findings improve upon our previously reported ANTHQ conversion efficiency on MONT and provide support for a plausible scenario in which PAH-mineral interactions could have produced prebiotically relevant quinones in early Earth environments.

Testing Abiotic Reduction of NAD+ Directly Mediated by Iron/Sulfur Minerals

Life emerged in a geochemical context, possibly in the midst of mineral substrates. However, it is not known to what extent minerals and dissolved inorganic ions could have facilitated the evolution of biochemical reactions. Herein, we have experimentally shown that iron sulfide minerals can act as electron transfer agents for the reduction of the ubiquitous biological protein cofactor nicotinamide adenine dinucleotide (NAD⁺) under anaerobic prebiotic conditions, observing the NAD⁺/NADH redox transition by using ultraviolet-visible spectroscopy and ¹H nuclear magnetic resonance. This reaction was mediated with iron sulfide minerals, which were likely abundant on early Earth in seafloor and hydrothermal settings; and the NAD⁺/NADH redox reaction occurred in the absence of UV light, peptide ligand(s), or dissolved mediators. To better understand this reaction, thermodynamic modeling was also performed. The ability of an iron sulfide mineral to transfer electrons to a biochemical cofactor that is found in every living cell demonstrates how geologic materials could have played a direct role in the evolution of certain cofactor-driven metabolic pathways.

A Proposed Geobiology-Driven Nomenclature for Astrobiological In Situ Observations and Sample Analyses

As the exploration of Mars and other worlds for signs of life has increased, the need for a common nomenclature and consensus has become significantly important for proper identification of nonterrestrial/non-Earth biology, biogenic structures, and chemical processes generated from biological processes. The fact that Earth is our single data point for all life, diversity, and evolution means that there is an inherent bias toward life as we know it through our own planet's history. The search for life "as we don't know it" then brings this bias forward to decision-making regarding mission instruments and payloads. Understandably, this leads to several top-level scientific, theoretical, and philosophical questions regarding the definition of life and what it means for future life detection missions. How can we decide on how and where to detect known and unknown signs of life with a single biased data point? What features could act as universal biosignatures that support Darwinian evolution in the geological context of nonterrestrial time lines? The purpose of this article is to generate an improved nomenclature for terrestrial features that have mineral/microbial interactions within structures and to confirm which features can only exist from life (biotic), features that are modified by biological processes (biogenic), features that life does not affect (abiotic), and properties that can exist or not regardless of the presence of biology (abiogenic). These four categories are critical in understanding and deciphering future returned samples from Mars, signs of potential extinct/ancient and extant life on Mars, and in situ analyses from ocean worlds to distinguish and separate what physical structures and chemical patterns are due to life and which are not. Moreover, we discuss hypothetical detection and preservation environments for extant and extinct life, respectively. These proposed environments will take into account independent active and ancient in situ detection prospects by using previous planetary exploration studies and discuss the geobiological implications within an astrobiological context.

Effects of Amino Acids on Iron-Silicate Chemical Garden Precipitation

Understanding the structure and behavior of chemical gardens is of interest for materials science, for understanding organic-mineral interactions, and for simulating geological mineral structures in hydrothermal systems on Earth and other worlds. Herein, we explored the effects of amino acids on inorganic chemical garden precipitate systems of iron chloride and sodium silicate to determine if/how the addition of organics can affect self-assembling morphologies or crystal growth. Amino acids affect chemical garden growth and morphology at the macro-scale and at the nanoscale. In this reaction system, the concentration of amino acid had a greater impact than the amino acid side chain, and increasing concentrations of organics caused structures to have smoother exteriors as amino acids accumulated on the outside surface. These results provide an example of how organic compounds can become incorporated into and influence the growth of inorganic self-organizing precipitates in far-from-equilibrium systems. Additionally, sample handing methods were developed to successfully image these delicate structures.

Bench-Stable Nickel Precatalysts with Heck-type Activation

Herein, we report the synthesis and characterization of a new class of air- and moisture-stable phosphine-containing nickel(II) precatalysts, which activate through a Heck-type mechanism. The activities of the precatalysts are demonstrated with a carbonyl–ene coupling reaction.

Bench-Stable N-Heterocyclic Carbene Nickel Precatalysts for C-C and C-N Bond-Forming Reactions

Herein, we introduce a new class of bench-stable N-heterocyclic carbene (NHC) nickel-precatalysts for homogeneous nickel-catalysis. The nickel(II) complexes are readily activated to Ni0 in situ under mild conditions, via a proposed Heck-type mechanism. The precatalysts are shown to facilitate carbonyl-ene, hydroalkenylation, and amination reactions.

A phase II clinical trial of sunitinib following hepatic transarterial embolization for metastatic neuroendocrine tumors

BACKGROUND

The liver is the predominant site of metastases among patients with advanced neuroendocrine tumors (NETs). Prior retrospective studies have reported high response rates in patients treated with transarterial embolization (TAE). NETs are highly vascular and are known to express vascular endothelial growth factor (VEGF) and vascular endothelial growth factor receptor (VEGFR). We hypothesized that administration of sunitinib, a VEGFR inhibitor, following TAE would extend progression-free survival (PFS).

PATIENTS AND METHODS

Patients with metastatic NETs to the liver underwent a series of selective TAEs followed by sunitinib (until disease progression or maximum of 12 months). Radiographic response (by RECIST), survival, and safety parameters were monitored.

RESULTS

Thirty-nine patients were enrolled. The overall response rate was 72% [95% confidence interval (CI), 0.58-0.86]. Median PFS was 15.2 months. Rates of overall survival (OS) at 1 and 4 years were 95% (95% CI, 0.88-1.00) and 59% (95% CI, 0.38-0.80), respectively. A significant 34% rise in serum VEGF was observed following the initial TAE (P = 0.03).

CONCLUSIONS

Hepatic TAE is a highly active treatment option for patients with metastatic NETs to the liver. Embolization stimulates release of VEGF into the circulation. Sunitinib, an oral VEGFR inhibitor, can be safely administered following embolization. The high rates of PFS and OS associated with this sequence of therapies are encouraging.

Nonsteroidal anti-inflammatory drug hypersensitivity syndrome: a multicenter study. II. Basophil activation by nonsteroidal anti-inflammatory drugs and its impact on pathogenesis

BACKGROUND

Patients who are clinically hypersensitive to nonsteroidal anti-inflammatory drugs (NSAIDs) sometimes present basophil activation in vitro, and in 50% of cases a parallel response to release of sulfidoleukotrienes (cellular allergen stimulation test) is observed. These phenomena occur not only in clinically hypersensitive patients, but also in some healthy controls who tolerate NSAIDs.

MATERIAL AND METHODS

We studied 16 clinically hypersensitive patients, 22 controls tolerating NSAIDs, and 29 healthy blood donors (clinical NSAID status unknown) using 2 different basophil isolation techniques (buffy coat or plasma leukocytes).

RESULTS

In a population of 13 aspirin-tolerant healthy controls and 29 healthy blood donors, basophil activation with aspirin, diclofenac, and naproxen was analyzed at 4 different concentrations. The results in the 2 groups were quite similar in qualitative terms. Choosing a cutoff of 5% and a stimulation index >2, the proportion of positive results increased with the concentration. There were more positive results at all concentrations using the plasma leukocyte technique.

CONCLUSIONS

The most important finding of this study is that basophil activation by NSAIDs occurs not only in clinically hypersensitive patients but also, to a very variable extent and on an individual basis, in apparently normal healthy individuals who tolerate NSAIDs. The phenomenon is clearly dose-related, and hypersensitive patients seem to react to lower NSAID concentrations.

Nonsteroidal anti-inflammatory drug hypersensitivity syndrome. A multicenter study. I. Clinical findings and in vitro diagnosis

BACKGROUND

We present the results obtained from the largest series of in vitro diagnostic tests ever reported in patients with clinically validated hypersensitivity to acetylsalicylic acid (ASA)/nonsteroidal anti-inflammatory drugs (NSAID) compared with various categories of controls tolerating ASA/NSAIDs. This multicenter study, which was performed within the framework of the European Network for Drug Allergy (ENDA) group, showed that the basophil activation test (BAT), particularly when used with the 3 NSAIDs aspirin (ASA), diclofenac (DIC), and naproxen (NAP), allows us to confirm the diagnosis of NSAID hypersensitivity syndrome. The results of the cellular allergen stimulation test (CAST) frequently correlate with those of the BAT, although not always. An unexpected finding was that basophil activation by NSAIDs is not an all-or-nothing phenomenon restricted to clinically hypersensitive patients, but that it also occurs in a dose-related manner in some NSAID-tolerant control individuals.Therefore, NSAID hypersensitivity appears as a shift in the normal pharmacological response to NSAIDs. These findings allow us to formulate a new rational hypothesis about the mechanism of NSAID hypersensitivity syndrome, a mechanism that most authors continue to describe as "unknown."

METHODS

We enrolled 152 patients with a history of hypersensitivity to NSAIDs and 136 control participants in 11 different centers between spring 2003 and spring 2006. Flowcytometric BAT was performed.

RESULTS

The most noteworthy results of our study were that 57% of 140 patients presented very clear-cut positive BAT results to multiple NSAIDs, and 16% were entirely negative. In about 27% of cases, positive results were obtained with 1 or 2 concentrations of a single NSAID. There is clearly a correlation between the results of BAT and CAST.

CONCLUSIONS

BAT seems particularly indicated in patients with a clinical history of NSAID intolerance, and in whom a provocation test is not advisable for ethical, clinical, or other reasons. Clear-cut positive results can be considered as confirming a history of NSAID hypersensitivity, although negative results may not exclude it.

Diagnosis of immediate-type beta-lactam allergy in vitro by flow-cytometric basophil activation test and sulfidoleukotriene production: a multicenter study

INTRODUCTION

This multicenter study aimed to evaluate the diagnostic value of 2 cellular tests based on basophil reactivity--the basophil activation test (BAT, Flow-CAST) and the sulfidoleukotriene release assay (CAST-ELISA)--in immediate-type beta-lactam allergy, particularly in patients with a clinical history of allergy and a negative skin test result.

MATERIAL AND METHODS

In a multicenter study encompassing 10 European centers, 181 patients with a history of immediate-type beta-lactam allergy, and 81 controls, we evaluated the diagnostic efficiency of specific IgE determinations and of 2 cellular tests based on basophil reactivity, the BAT and the sulfidoleukotriene release assay.

RESULTS

With Flow-CAST, sensitivity varied for individual beta-lactam allergens from 16% for penicilloyl-polylysine to 33% for amoxicillin, reaching 50% when all 5 allergens were considered. In beta-lactam-allergic patients with negative skin test results (22.8%), Flow-CAST showed positive results for at least 1 of the 5 allergens in 37%. Specificity varied from 89% to 97%, depending on the allergens used. In CAST-ELISA, the overall sensitivity in skin test-positive patients was 41.7%; in patients with negative skin test results it was 27.9%. Both tests were not absolutely correlated, so that when all the results were considered together, sensitivity increased to 64.3% and specificity varied for both tests combined from 73% to 92%. In contrast, specific IgE determinations in the same population yielded a lower sensitivity (28.3%).

CONCLUSIONS

A diagnostic algorithm including skin tests and specific IgE, followed by cellular tests in negative patients and controlled challenge enabled us to confirm beta-lactam allergy in 92% of cases. This procedure would also allow us to avoid two-thirds of the required controlled challenges.

Predictive value of the sulfidoleukotriene release assay in oral allergy syndrome to celery, hazelnut, and carrot

BACKGROUND

Patients sensitized to birch pollen frequently suffer from a food allergy to plant foods such as celery, carrots, or hazelnut. One of the main manifestations of birch pollen-related food allergy is the oral allergy syndrome. Skin tests and allergen-specific immunoglobulin (Ig) E determinations are poor predictors of such reactions when assessed by double-blind placebo-controlled food challenge (DBPCFC).

OBJECTIVE

To investigate whether a cellular test based on leukotriene release from basophils, the cellular antigen stimulation test in combination with enzyme-linked immunosorbent assay (CAST-ELISA), is predictive of pollen-related food allergy.

METHODS

Birch pollen-sensitized patients with positive DBPCFC to celery (n=21), hazelnut (n=15), and carrot (n=7) underwent skin tests along with determination of specific IgE and CAST-ELISA for the respective allergens. The results were compared with those of 24 birch pollen-sensitized patients with negative open food challenge to celery, hazelnut, and carrot.

RESULTS

While skin prick tests had a sensitivity of 85%, 80%, and 29% for commercial extracts of celery, hazelnut, and carrot, respectively, prick testing with self-prepared extracts yielded sensitivities of 100%, 80%, and 100%, respectively. For specific IgE determinations, sensitivities were 71%, 73%, and 57%, respectively, and the respective specificities were 67%, 73%, and 60%. For CAST-ELISA with various sources and doses of allergens, the sensitivity varied from 71% to 95% for celery, 73% to 80% for hazelnut, and 43% to 86% for carrot. The respective specificities were 67% to 92%, 75% to 88%, and 77% to 91%. Analysis of the predictive value of CAST-ELISA with receiver operating characteristic curves showed that the results of the tests were more predictive of pollen-related food allergy than quantitative allergen-specific IgE determinations.

CONCLUSIONS

CAST-ELISA is more specific than routine diagnostic tests for the diagnosis of pollen-related food allergy to celery, hazelnut, and carrot.

Echinococcus multlocularis infections of rural, residential and urban foxes (Vulpes vulpes) in the canton of Geneva, Switzerland

We examined 267 red foxes (Vulpes vulpes) from the canton of Geneva, Switzerland, for intestinal infections with Echinococcus multilocularis. This region is situated in the core area of the endemic range of this zoonotic cestode in Central Europe. Several factors were taken into account and urbanisation level appeared to be the most explicative to describe observed differences. The prevalence decreased significantly from rural and residential areas (prevalence of 52%, CI 43-62%, and 49%, CI 38-59 %, respectively) to the urban area (prevalence of 31%, CI 19-42%). A few juvenile foxes harboured very high burdens up to more than 120,000 worms and were significantly more heavily infected than adults. The intensity of infection decreased from rural and residential areas to the city, suggesting a lower contamination of the urban environment.

Photodetachment spectroscopy of PtBr42−: Probing the Coulomb barrier of a doubly charged anion

We probe the repulsive Coulomb barrier of the doubly charged anion PtBr(4) (2-) by photodetachment spectroscopy. The results are discussed in terms of models for the photoemission process, the excitation spectrum of PtBr(4) (2-), and calculations of the energy-dependent tunneling probability for various model potentials.

An Infrared Investigation of the (CO2)n- Clusters: Core Ion Switching from Both the Ion and Solvent Perspectives

The (CO2)n- clusters are thought to accommodate the excess electron by forming a localized molecular anion, or "core ion", solvated by the remaining, largely neutral CO2 molecules. Earlier studies interpreted discontinuities in the (CO2)n- photoelectron spectra to indicate that both the CO2- and C2O4- species were present in a size-dependent fashion. Here we use vibrational predissociation spectroscopy to unambiguously establish the molecular structures of the core ions in the 2 < or = n < or = 17 size range. Spectra are reported in the 2300-3800 cm(-1) region, which allows us to independently monitor the contribution of each ion through its characteristic overtone and combination bands. These signature bands are observed to be essentially intact in the larger clusters, establishing that the CO2- and C2O4- molecular ions are indeed the only electron accommodation modes at play. The size dependence of the core ion suggested in earlier analyses of the photoelectron spectra is largely confirmed, although both species are present over a range of clusters near the expected critical cluster sizes, as opposed to the prompt changes inferred earlier. Perturbations in the bands associated with the nominally neutral CO2 "solvent" molecules are correlated with the changes in the molecular structure of the core ion. These observations are discussed in the context of a diabatic model for electron delocalization over the CO2 dimer. In this picture, the driving force leading to the transient formation of the monomer ion is traced to the solvent asymmetry inherent in an incomplete coordination shell.

Constitutively active PTH/PTHrP receptor in odontoblasts alters odontoblast and ameloblast function and maturation

Parathyroid hormone (PTH)-related protein (PTH-rP) is an important autocrine/paracrine attenuator of programmed cell differentiation whose expression is restricted to the epithelial layer in tooth development. The PTH/PTHrP receptor (PPR) mRNA in contrast is detected in the dental papilla, suggesting that PTHrP and the PPR may modulate epithelial-mesenchymal interactions. To explore the possible interactions, we studied the previously described transgenic mice in which a constitutively active PPR is targeted to osteoblastic cells. These transgenic mice have a vivid postnatal bone and tooth phenotype, with normal tooth eruption but abnormal, widened crowns. Transgene mRNA expression was first detected at birth in the dental papilla and, at 1 week postnatally, in odontoblasts. There was no transgene expression in ameloblasts or in other epithelial structures. Prenatally, transgenic molars and incisors revealed no remarkable change. By the age of 1 week, the dental papilla was widened, with disorganization of the odontoblastic layer and decreased dentin matrix. In addition, the number of cusps was abnormally increased, the ameloblastic layer disorganized, and enamel matrix decreased. Odontoblastic and, surprisingly, ameloblastic cytodifferentiation was impaired, as shown by in situ hybridization and electron microscopy. Interestingly, ameloblastic expression of Sonic Hedgehog, a major determinant of ameloblastic cytodifferentiation, was dramatically altered in the transgenic molars. These data suggest that odontoblastic activation of the PPR may play an important role in terminal odontoblastic and, indirectly, ameloblastic cytodifferentiation, and describe a useful model to study how this novel action of the PPR may modulate mesenchymal/epithelial interactions at later stages of tooth morphogenesis and development.

Osteoblastic cells regulate the haematopoietic stem cell niche

Stem cell fate is influenced by specialized microenvironments that remain poorly defined in mammals. To explore the possibility that haematopoietic stem cells derive regulatory information from bone, accounting for the localization of haematopoiesis in bone marrow, we assessed mice that were genetically altered to produce osteoblast-specific, activated PTH/PTHrP receptors (PPRs). Here we show that PPR-stimulated osteoblastic cells that are increased in number produce high levels of the Notch ligand jagged 1 and support an increase in the number of haematopoietic stem cells with evidence of Notch1 activation in vivo. Furthermore, ligand-dependent activation of PPR with parathyroid hormone (PTH) increased the number of osteoblasts in stromal cultures, and augmented ex vivo primitive haematopoietic cell growth that was abrogated by gamma-secretase inhibition of Notch activation. An increase in the number of stem cells was observed in wild-type animals after PTH injection, and survival after bone marrow transplantation was markedly improved. Therefore, osteoblastic cells are a regulatory component of the haematopoietic stem cell niche in vivo that influences stem cell function through Notch activation. Niche constituent cells or signalling pathways provide pharmacological targets with therapeutic potential for stem-cell-based therapies.

Anaphylaxis to the carbohydrate carboxymethylcellulose in parenteral corticosteroid preparations

BACKGROUND

Carboxymethylcellulose is a carbohydrate widely used as additive in tablets, cosmetics, some injectable hormone formulations, food (as E466) and as active principle in hydrocolloid dressings. Anaphylaxis to carboxymethylcellulose in parenteral corticosteroid preparations has previously been reported. Typically, skin tests were positive in such cases, occasionally specific IgE or histamine release have been demonstrated.

CASE REPORT

We report on 3 patients who suffered from anaphylactic symptoms after local injection of corticosteroid preparations. Intracutaneous skin tests with carboxymethylcellulose were positive; in 2, sulfidoleukotriene release could be measured in the cellular antigen stimulation test (CAST). Specific IgE could not be identified. Oral provocation tests with typical doses of carboxymethylcellulose as found in food and tablets were negative.

CONCLUSION

In patients with anaphylaxis to parenteral administration of carboxymethylcellulose, small amounts are tolerated by the oral route. Skin tests and CAST are useful diagnostic tools.

Optimization of 4-phenylamino-3-quinolinecarbonitriles as potent inhibitors of Src kinase activity

Subsequent to the discovery of 4-[(2,4-dichlorophenyl)amino]-6,7-dimethoxy-3-quinolinecarbonitrile (1a) as an inhibitor of Src kinase activity (IC(50) = 30 nM), several additional analogues were prepared. Optimization of the C-4 anilino group of 1a led to 1c, which contains a 2,4-dichloro-5-methoxy-substituted aniline. Replacement of the methoxy group at C-7 of 1c with a 3-(morpholin-4-yl)propoxy group provided 2c, resulting in increased inhibition of both Src kinase activity and Src-mediated cell proliferation. Analogues of 2c with other trisubstituted anilines at C-4 were also potent Src inhibitors, and the propoxy group of 2c was preferred over ethoxy, butoxy, or pentoxy. Replacement of the morpholine group of 2c with a 4-methylpiperazine group provided 31a, which had an IC(50) of 1.2 nM in the Src enzymatic assay, an IC(50) of 100 nM for the inhibition of Src-dependent cell proliferation and was selective for Src over non-Src family kinases. Compound 31a, which had higher 1 and 4 h plasma levels than 2c, effectively inhibited tumor growth in xenograft models.

High-altitude acclimation increases the triacylglycerol/fatty acid cycle at rest and during exercise

High-altitude acclimation alters lipid metabolism during exercise, but it is unknown whether this involves changes in rates of lipolysis or reesterification, which form the triacylglycerol/fatty acid (TAG/FA) cycle. We combined indirect calorimetry with [2-(3)H]glycerol and [1-(14)C]palmitate infusions to simultaneously measure total lipid oxidation, lipolysis, and rate of appearance (R(a)) of nonesterified fatty acids (NEFA) in high-altitude-acclimated (HA) rats exercising at 60% maximal O(2) uptake (VO(2 max)). During exercise, relative total lipid oxidation (%VO(2)) equaled sea-level control (SL) values; however, acclimation greatly stimulated lipolysis (+75%) but had no effect on R(a) NEFA. As a result, TAG/FA cycling increased (+119%), due solely to an increase in recycling (+144%) within adipocytes. There was no change in either group in these variables with the transition from rest to exercise. We conclude that, in HA, 1) acclimation is a potent stimulator of lipolysis; 2) rats do not modify TAG/FA cycling with the transition to exercise; and 3) in normoxia, HA and SL derive the same fraction of their total energy from lipids and carbohydrates.

Interactions of human lacrimal and salivary cystatins with adenovirus endopeptidase

Over 100 serotypes of adenoviruses have been implicated in a variety of human and domesticated animal pathologies and some serotypes are widely used as gene transfer vectors. Aside from the limited use of vaccines for specific serotypes, little effort has been expended in the development of antivirals. The objective here was to study the effect of cystatins from human saliva (CS) and tears (CT), two points of viral entry, on adenain, the adenovirus type 2 encoded proteinase, which is absolutely required for infectivity. Two molecular weight species (13 and 14.5 kDa) were purified from both fluids at a yield of 5 mg/l. In vitro adenain activity was inhibited to 50% at a molar ratio of 5 CS:1 adenain and 3 CT:1 adenain. By comparison, papain was inhibited to 50% at a molar ratio of 2 CS:1 papain and 1.5 CT:1 papain. Adenain differed from papain in response to CS and chicken egg white (CEW) cystatin in being stimulated at low concentrations, and in being inhibited only at very high concentrations of cystatins. The presence of cleavage consensus sites specific to adenain in the human cystatins could drive the adenain-cystatin interaction predominantly in the substrate pathway direction. However, we found that the cystatins could only be digested after denaturation and by highly active fresh enzyme preparations. Our experiments designed to test the nature of the interaction between adenain and cystatins suggest a docking model for the adenain-human cystatin interaction, similar to that proposed for papain and CEW. At equilibrium the dissociation constant, K(d), between adenain and CT was 1.2 nM. The kinetic parameters determined here suggest a simple reversible mechanism for the inhibition of adenain by human cystatins. We conclude that the cystatins present in tears and saliva are unlikely to play a significant role in inhibiting adenovirus infections.

Antibiotic prophylaxis for group A streptococcal burn wound infection is not necessary

BACKGROUND

Historically, group A beta-hemolytic streptococci (GAS) burn wound infection has been a major source of morbidity and mortality in burn patients and has prompted the prophylactic administration of antibiotics to children with burns. Wound monitoring, surveillance cultures, and early excision of deep wounds may have changed this. Our objective in this project was to determine the efficacy of routine antibiotic prophylaxis in the era of early excision and closure of deep burn wounds.

METHODS

Two cohorts of burned children were compared: all children admitted during calendar years 1992 through 1994 (group 1) and during calendar years 1995 through 1997 (group 2). All group 1 children received routine GAS antibiotic prophylaxis. Only those group 2 children with documented positive admission or surveillance cultures for GAS were treated.

RESULTS

There were 511 children in group 1 and 406 children in group 2. They were well matched for age (4.7 +/- 0.21 years vs. 5.3 +/- 0.26 years, p = 0.06) and burn size (11.0% +/- 0.7% vs. 12.4% +/- 0.8%, p = 0.18). GAS species were recovered at admission or during hospitalization from 11 (2.6%) of group 1 children and 18 (4.4%) of group 2 children (p = 0.05), indicating a marginally higher rate of carriage in group 2. Nevertheless, in group 1 there were three (0.6%) who developed GAS wound infection and in group 2 there were four (0.98%, p = 0.71). The incidence of GAS infection in those patients with positive admission cultures was three (27%) of group 1 and four (22%) of group 2. No child developed fulminant GAS infection.

CONCLUSION

Routine antibiotic prophylaxis of burn wounds in children in not effective in further reducing a low baseline incidence of GAS wound infection if admission screening by culture is used to identify those children who carry the organism and early excision of deep burns is practiced.

Synthesis and Src kinase inhibitory activity of a series of 4-phenylamino-3-quinolinecarbonitriles

Screening of a directed compound library in a yeast-based assay identified 4-[(2,4-dichlorophenyl)amino]-6,7-dimethoxy-3-quinolinecarbonitrile (2a) as a Src inhibitor. An enzymatic assay established that 2a was an ATP-competitive inhibitor of the kinase activity of Src. We present here SAR data for 2a which shows that the aniline group at C-4, the carbonitrile group at C-3, and the alkoxy groups at C-6 and C-7 of the quinoline are crucial for optimal activity. Increasing the size of the C-2 substituent of the aniline at C-4 of 2a from chloro to bromo to iodo resulted in a corresponding increase in Src inhibition. Furthermore, replacement of the 7-methoxy group of 2a with various 3-heteroalkylaminopropoxy groups provided increased inhibition of both Src enzymatic and cellular activity. Compound 25, which contains a 3-morpholinopropoxy group, had an IC(50) of 3.8 nM in the Src enzymatic assay and an IC(50) of 940 nM for the inhibition of Src-dependent cell proliferation.

Inhibitors of src tyrosine kinase: the preparation and structure-activity relationship of 4-anilino-3-cyanoquinolines and 4-anilinoquinazolines

Src is a nonreceptor tyrosine kinase involved in signaling pathways that control proliferation, migration, and angiogenesis. Increased Src expression and activity are associated with an increase in tumor malignancy and poor prognosis. Several quinolines and quinazolines were identified as potent and selective inhibitors of Src kinase activity.

Cutaneous herpetic infections complicating burns

Many people harbor herpes simplex virus, often with a known history of "cold sores". During the relatively immunosuppressed state associated with a serious burn, recrudescence of such infections can occur. We report four adults and two children who developed severe herpetic ulceration, over the face and neck in five patients and in a partial thickness wound in one patient. Herpetic infection was diagnosed by culture and direct immunofluorescence testing and treatment was immediately instituted with systemic and topical Acylovir(R) (Zovirax, Glaxo Wellcome). Ulceration healed under treatment and did not leave visible scarring in any of the patients. Although these infections are rapidly progressive, they respond to prompt treatment with antiviral chemotherapy. Rapidly progressive vesicles and ulceration appearing on the face or in the wounds of burn patients should prompt immediate evaluation for herpetic infection.

The human circadian pacemaker can see by the dawn's early light

The authors' previous experiments have shown that dawn simulation at low light intensities can phase advance the circadian rhythm of melatonin in humans. The aim of this study was to compare the effect of repeated dawn signals on the phase position of circadian rhythms in healthy participants kept under controlled light conditions. Nine men participated in two 9-day laboratory sessions under an LD cycle 17.5:6.5 h, < 30:0 lux, receiving 6 consecutive daily dawn (average illuminance 155 lux) or control light (0.1 lux) signals from 0600 to 0730 h (crossover, random-order design). Two modified constant routine protocols before and after the light stimuli measured salivary melatonin (dim light melatonin onset DLMOn and offset DLMOff) and rectal temperature rhythms (midrange crossing time [MRCT]). Compared with initial values, participants significantly phase delayed after 6 days under control light conditions (at least -42 min DLMOn, -54 min DLMOff, -41 min MRCT) in spite of constant bedtimes. This delay was not observed with dawn signals (+10 min DLMOn, +2 min DLMOff, 0 min MRCT). Given that the endogenous circadian period of the human circadian pacemaker is slightly longer than 24 h, the findings suggest that a naturalistic dawn signal is sufficient to forestall this natural delay drift. Zeitgeber transduction and circadian system response are hypothesized to be tuned to the time-rate-of-change of naturalistic twilight signals.

Phase advance after one or three simulated dawns in humans

A specially designed apparatus that can simulate the waveform of the dawn or dusk signal at any latitude and any day of the year has been shown to phase shift the circadian pacemaker in rodents and primates at a fraction of the illuminance previously used. Until recently, it was considered that rather high illuminances or rather long exposure episodes to room light were necessary to phase shift human circadian rhythms. This experiment shows that, under controlled conditions of a modified constant routine protocol, a single dawn signal is sufficient to phase advance the timing of the onset of secretion of the pineal hormone melatonin. The significant phase advance of salivary melatonin of 20 minutes, which is enhanced to 34 minutes after three consecutive dawn signals, is small, but appears to be of sufficient magnitude to entrain the human circadian pacemaker, which has an endogenous period of about 24.2h.

Protease-deleted adenovirus vectors and complementing cell lines: potential applications of single-round replication mutants for vaccination and gene therapy

A new kind of versatile adenoviral vector (AdV) has been constructed, one that is completely replication disabled in the absence of Ad-E1 proteins but is capable of a single round of replication when Ad-E1 is present. This was made possible by deletion of the Ad protease gene (PS), which is essential for many steps of the Ad life cycle. The PS-deleted virus can be propagated in 293-derived cell lines engineered to express PS. In these new complementing cells, the PS gene was expressed from a tetracycline-inducible promoter in a dicistronic vector coexpressing the green fluorescent protein (GFP). When induced, the best 293-PS stable clones produced the PS in amounts greater than the level reached after Ad infection. Biological activity was first demonstrated by the ability of 293-PS cells to support the replication of Ad2ts1, a mutant expressing a functionally defective PS. While overexpression of the Ad PS slightly affected cell growth, moderate expression at levels sufficient to fully complement Ad2ts1 was well tolerated in 293 cells. Two PS-deleted mutants, deleted or not deleted for E1/E3, were then generated and characterized. Despite their complete loss of infectivity after a single round of replication in permissive cells, the PS-deleted mutants produced as much viral protein as wildtype Ad. These new vectors should thus be both safer and more efficient for applications in which enhancement of transgene expression is desirable, as in the case of vaccination, in situ therapy for tumors, protein production, or the large-scale production of other viral vectors such as adeno-associated virus (AAV).

The effect of mutant peptide cofactors on adenovirus protease activity and virus infection

Adenoviruses encode a cysteine protease, adenain, required for uncoating and virion maturation. Adenain activity is regulated by an 11-amino-acid peptide cofactor thiol-bonded distal to the active site. Structural and experimental data suggest that the peptide might stabilize adenain in an optimal conformation for enzyme activity by bridging two noncontiguous regions of the molecule. The sequence requirements for this mechanism were examined both in vitro and ex vivo by means of mutant peptides and databank analysis. The results of in vitro experiments suggested that activation is not an all or nothing mechanism. With the exception of the smallest peptide, the mutant peptides bound to adenain, activated it, and competed with the wild-type peptide, but all of this occurred with reduced efficiency. When added to the medium of infected cells, most of the peptides inhibited infectious virus production to varying degrees in a dose-dependent manner and in accordance with their in vitro activity on adenain. We interpret this inhibition to be due to unscheduled adenain activation. Examination of the activation peptide sequences from 19 adenovirus serotypes revealed a limited number of conserved sequence features. These features were in agreement with the experimental data. We conclude that binding and activation of adenain by pVIc may be reversible and this reversibility may be an integral aspect of the in vivo regulation of enzyme activity in the course of virus assembly. The peptide cofactor binding domain is therefore a potential target for the development of anti-adenoviral agents.

Energy metabolism of the Virginia opossum during fasting and exercise

Rates of oxygen consumption and CO(2) production were measured in Virginia opossums (Didelphis virginiana) during fasting and prolonged exercise to quantify changes in total energy expenditure and oxidative fuel selection. We hypothesized that fasting would cause metabolic depression and a progressive shift towards lipid utilization to spare alternative substrates. It was also predicted that prolonged exercise would cause the same relative changes in fuel preference as fasting, but on a compressed time scale. The results show that hypometabolism is not used by the Virginia opossum to cope with food deprivation. However, a rapid exhaustion of limited carbohydrate reserves is prevented through a sixfold reduction in the percentage contribution of carbohydrates to total energy expenditure made possible by an increase in lipid utilization. No protein sparing is observed in this species. Prolonged low-intensity exercise elicits a potent mobilization of lipids that allows maximal running time to be extended by delaying the depletion of limited carbohydrate reserves. We conclude that fasting and prolonged low-intensity exercise cause similar changes in the relative use of lipids and carbohydrates, but on a different time scale, supporting the idea that endurance exercise is the metabolic equivalent of ‘accelerated fasting’. The absence of metabolic depression and protein sparing during fasting shows that such physiological strategies have not been necessary for the rapid range expansion towards the North recently shown by this species.

Regulation of glucose production in rainbow trout: role of epinephrine in vivo and in isolated hepatocytes

The rate of hepatic glucose production (R(a) glucose) of rainbow trout (Oncorhynchus mykiss) was measured in vivo by continuous infusion of [6-(3)H]glucose and in vitro on isolated hepatocytes to examine the role of epinephrine (Epi) in its regulation. By elevating Epi concentration and/or blocking beta-adrenoreceptors with propranolol (Prop), our goals were to investigate the mechanism for Epi-induced hyperglycemia to determine the possible role played by basal Epi concentration in maintaining resting R(a) glucose and to assess indirect effects of Epi in the intact animal. In vivo infusion of Epi caused hyperglycemia (3.75 +/- 0.16 to 8.75 +/- 0.54 mM) and a twofold increase in R(a) glucose (6.57 +/- 0.79 to 13.30 +/- 1.78 micromol. kg(-1). min(-1), n = 7), whereas Prop infusion decreased R(a) from 7.65 +/- 0.92 to 4.10 +/- 0.56 micromol. kg(-1). min(-1) (n = 10). Isolated hepatocytes increased glucose production when treated with Epi, and this response was abolished in the presence of Prop. We conclude that Epi-induced trout hyperglycemia is entirely caused by an increase in R(a) glucose, because the decrease in the rate of glucose disappearance normally seen in mammals does not occur in trout. Basal circulating levels of Epi are involved in maintaining resting R(a) glucose. Epi stimulates in vitro glucose production in a dose-dependent manner, and its effects are mainly mediated by beta-adrenoreceptors. Isolated trout hepatocytes produce glucose at one-half the basal rate measured in vivo, even when diet, temperature, and body size are standardized, and basal circulating Epi is responsible for part of this discrepancy. The relative increase in R(a) glucose after Epi stimulation is similar in vivo and in vitro, suggesting that indirect in vivo effects of Epi, such as changes in hepatic blood flow or in other circulating hormones, do not play an important role in the regulation of glucose production in trout.

Isolating the spectroscopic signature of a hydration shell with the use of clusters: superoxide tetrahydrate

Cluster spectroscopy, aided by ab initio theory, was used to determine the detailed structure of a complete hydration shell around an anion. Infrared spectra of size-selected O(2)-. (H(2)O)(n) (n = 1 to 4) cluster ions were obtained by photoevaporation of an argon nanomatrix. Four water molecules are required to complete the coordination shell. The simple spectrum of the tetrahydrate reveals a structure in which each water molecule is engaged in a single hydrogen bond to one of the four lobes of the pi* orbital of the superoxide, whereas the water molecules bind together in pairs. This illustrates how water networks deform upon accommodating a solute ion to create a distinct supramolecular species.

Adenovirus endopeptidase hydrolyses human squamous cell carcinoma antigens in vitro but not ex vivo

The serpins SCCA1 and SCCA2 are highly expressed in the epithelium of the conducting airways, a common site of infection by group C adenoviruses, such as human adenovirus type 2 (Ad2). Based on the common location we examined a possible interaction between them. In vitro experiments with recombinant proteins showed that SCCA1 inhibited the viral protease in a dose-dependent manner. Both serpins were cleaved in a manner consistent with hydrolysis within their reactive site loop, without the formation of an SDS-resistant complex, as in the case of papain. Infection of SCCA1-expressing cells did not result in the cleavage of SCCA1, nor was the yield of infectious virus affected as compared to SCCA1-negative parental cells. This may be due to differential localization, the serpin being cytoplasmic and viral protease being nuclear. Surprisingly, however, virus infection, which tends to inhibit host protein synthesis, caused a significant increase in SCCA1 expression well into the late phase of infection.

Effect of high-altitude acclimation on NEFA turnover and lipid utilization during exercise in rats

Relative exercise intensity (or %maximum O(2) consumption, VO(2 max)) controls fuel selection at sea level (SL) and after high-altitude acclimation (HA) in rats. In this context we used indirect calorimetry, [1-(14)C]palmitate infusions, and muscle triacylglycerol (TAG) measurements to determine 1) total lipid oxidation, 2) the relationship between circulatory nonesterified fatty acid (NEFA) flux and concentration, and 3) muscle TAG depletion after exercise in HA-acclimated rats. Aerobic capacity is decreased in trained rats after 10 wk of acclimation. Both SL and HA showed the same relative use of lipids at 60% [62 +/- 5% (HA) and 61 +/- 3% (SL) of O(2) consumption (VO(2))] and 80% [46 +/- 6% (HA) and 47 +/- 5% (SL) of VO(2)] of their respective VO(2 max). At 60% VO(2 max), plasma [NEFA] were higher in HA, but rate of appearance was essentially the same in both groups (at 30 min, 38 +/- 9 vs. 49 +/- 6 micromol. kg(-1). min(-1) in HA and SL, respectively). At this intensity SL showed no significant decrease in muscle TAG, but in HA it decreased by 64% in soleus and by 90% in red gastrocnemius. We conclude that 1) the relative contributions of total lipid are the same in SL and HA, contrary to differences in [NEFA], because the relationship between flux rate and [NEFA] is modified after acclimation, and 2) muscle TAG may play a more important role at HA.

Management of severe toxic epidermal necrolysis in children

Toxic epidermal necrolysis (TEN) is a severe form of erythema multiforme that results in extensive epidermal sloughing; the condition is associated with a mortality of up to 70%. From 1991 to 1998, 10 children with severe toxic epidermal necrolysis were referred to a regional pediatric burn facility. Wounds were managed with strategy involving prevention of wound desiccation and superinfection, including the frequent use of biologic wound coverings. Children unable to guard their airway because of extensive oropharyngeal involvement were prophylactically intubated. Enteral nutrition was stressed. Steroids were not used and antibiotics were administered to managed specific foci of infection only. The 2 boys and 8 girls had an average age of 7.2+/-1.8 years (range 6 months to 15 years) and sloughed surface area of 76+/-6% of the body surface (range 50 to 95%). Antibiotics (3 children), anticonvulsants (3 children), nonsteroidals (2 children), and viral syndrome or unknown agents (2 children) were felt to have triggered the syndrome. Six children (60%) required intubation for an average of 9.7+/-1.8 days (range 2 to 14 days). Buccal mucosal involvement occurred in 9 (90%) and ocular involvement in 9 (90%). Although infectious complications were common (2 pneumonias, 2 urinary infections, 1 bacteremia, 2 central line infections, and 2 candidemias), all children survived after lengths of stay in the burn unit averaging 19+/-3 (range 6 to 40) days. The most common long-term morbidity was keratitis sicca (2 children, 20%), finger nail deformities (3 children, 30%), and variegated skin pigment changes (5 children, 50%). Although having both a cutaneous and visceral wound that predispose them to infectious complications, most children with TEN will survive if managed with a strategy emphasizing biologic wound closure, intensive nutritional support, and early detection and treatment of septic foci. Burn units have the resource set required to manage severe TEN and early referral of such children may have a favorable impact on survival.

Photodynamic therapy: tumor targeting with adenoviral proteins

A brief summary of the mechanisms involved in photodynamic therapy (PDT) and the role of delivery vehicles for photosensitizer targeting is addressed. Phthalocyanines (Pc) have been coupled to adenovirus type 2 capsid proteins including the hexon, the penton base and the fiber to enhance their target selectivity. Adenovirus penton base proteins contain the arginine-glycine-aspartic acid peptidic sequence (RGD) motif known to bind with great affinity and high specificity to integrin receptors, expressed by several types of cancer. Tetrasulfonated aluminum phthalocyanine (AlPcS4) was covalently coupled to the various capsid proteins via one or two caproic acid spacer chains (A1 or A2) in 7:1 up to 66:1 molar ratios. The capacity of the bioconjugates for singlet oxygen production, as measured by an L-tryptophan oxidation assay, was strongly reduced, likely reflecting scavenging by the carrier. Cell adsorption and in vitro photocytotoxicity assays were carried out using the A549 and HEp2 human cell lines expressing integrin receptors, and one murine, the EMT-6 cell line, which lacks receptors for the RGD sequence. The AlPcS4A2-protein complexes induced greater cytotoxicity as compared to the analogous AlPcS4A1 preparations. The penton base-AlPcS4A2 derivative was the more phototoxic for all cell lines tested. Tumor response studies using Balb/c mice with EMT-6 tumor implants demonstrated that the free AlPcS4A2 induced complete tumor regression at a dose of 1 mumol/kg and 400 J/cm2, which is comparable to the activity of the known AlPcS2adj. A mixture of adenovirus type 2 soluble proteins covalently labeled with AlPcS4A2 required 0.5 mumol/kg to induce the same response with the same light dose, suggesting that the high affinity RGD/receptor complex is able to target Pc for PDT.

Effects of sustained swimming on hepatic glucose production of rainbow trout

The rate of hepatic glucose production (R(a)glucose) was measured by continuous infusions of 6-[(3)H]glucose in live rainbow trout (Oncorhynchus mykiss) before, during and after swimming for 3 h at 1.5 body lengths s(−)(1) in a swim tunnel. Contrary to expectation, we found that sustained swimming causes a 33 % decline in the R(a),(glucose) of trout (from 7.6+/−2.1 to 5.1+/−1.3 (μ)mol kg(−)(1)min(−)(1), means +/− s.e.m., N=7), even though exercise of the same intensity elicits a two- to fourfold increase in all the mammalian species investigated to date. Measurements of catecholamine levels show that circulating [epinephrine] decreases by 30 % during exercise (from 4.7+/−0.3 to 3.3+/−0.4 nmol l(−)(1), N=8), suggesting that this hormone is partly responsible for controlling the decline in R(a)glucose. The inhibiting effect of swimming on hepatic glucose production persists for at least 1 h after the cessation of exercise. In addition, rainbow trout can maintain a steady blood glucose concentration throughout sustained exercise by closely matching hepatic glucose production with peripheral glucose utilization, even though this species is generally considered to be a poor glucoregulator. This study provides the first continuous measurements of glucose kinetics during the transition from rest to work in an ectotherm and it suggests that circulating glucose is not an important fuel for aerobic locomotion in trout.

A 15-year experience with varicella infections in a pediatric burn unit

Because of their well described global immunosuppression, varicella infection may be hazardous in burned children. It is therefore important to prevent cross-infections within pediatric burn units. We describe a 15-year experience with varicella in a pediatric burn unit, focusing on the morbidity associated with the infection and measures that have been effective in the prevention of cross-infection. We found that varicella infection in acutely burned children is associated with pneumonitis, but little wound related morbidity. Despite the deceptively long incubation period, prompt identification and isolation of index cases was associated with an extremely low incidence of cross-infection. Until widespread administration of varicella vaccine confers herd immunity, varicella remains a threat to hospitalized young children, highlighting the importance of a well planned and executed index case isolation strategy.

Adenovirus endopeptidase and papain are inhibited by the same agents

Adenoviruses encode a cysteine protease (AVP) which carries out highly specific cleavages on at least seven viral proteins and two cellular proteins. Virus infectivity is dependent on this function. The three-dimensional positions of the amino acids involved in catalysis display a striking similarity to those of papain, suggesting a similar catalytic mechanism. This similarity has prompted us to compare the effect of papain inhibitors on the two enzymes. AVP and papain activity was tested on a fluorescent peptide substrate as well as on metabolically labeled adenovirus (Ad2) precursor proteins. Hep2 cells infected with Ad2 were exposed to inhibitors and assayed for, (a) infectious virus, (b) in situ Ad2 protease activity, (c) physical particle production and their polypeptide composition. We found that in both substrate systems AVP was sensitive to the papain inhibitors benzamidoacetonitrile, acetamidoacetonitrile and N-methoxyphenylalanine glycylnitrile, and that the degree of sensitivity was influenced by the substrate. Unlike papain, AVP was relatively insensitive to E64. In ex vivo tests, Hep2 cells infected with Ad2 were exposed to inhibitors and assayed for, (a) infectious virus, (b) in situ Ad2 protease activity, (c) physical particle production and their polypeptide composition. A 4-fold reduction in virus titer was obtained when the inhibitors were added between 17 and 25 h after infection. Processing of precursor proteins was also inhibited yet the production of physical particles was only reduced 2-fold. These experiments show that papain inhibitors are also capable of inhibiting the adenovirus protease both in vitro and ex vivo, thus forging a possible link between structural similarity and functionality.

Carbohydrate utilization during exercise after high-altitude acclimation: a new perspective

At high altitude (HA), carbohydrate (CHO) is thought to be the preferred fuel because of its higher yield of ATP per mole of O2. We used indirect calorimetry and D-[6-3H]glucose infusions to determine total CHO and circulatory glucose utilization during exercise in HA-acclimated and sea level (SL) rats. We hypothesized that the percent contribution of CHO to total metabolism (VO2) is determined by exercise intensity relative to an aerobic maximum (% VO2max). HA rats run under hypoxia (FIO2 = 0.12) showed a decrease in VO2max compared with SL (67.55 +/- 1.26 vs. 89.30 +/- 1.23 ml kg-1 min-1). When exercised at 60% of their respective VO2max, both groups showed the same relative use of CHO (38 +/- 3% and 38 +/- 5% of VO2, at the beginning of exercise, in HA and SL, respectively). In both HA and SL, circulatory glucose accounted for approximately 20% of VO2, the balance was provided by muscle glycogen (approximately 18% of VO2). After 20 min at a higher intensity of 80% VO2max, 54 +/- 5% (HA) and 59 +/- 4% (SL) of VO2 was accounted for by CHO. We conclude the following: (i) the relative contributions of total CHO, circulatory glucose, and muscle glycogen do not increase after HA acclimation because the O2-saving advantage of CHO is outweighed by limited CHO stores; and (ii) relative exercise intensity is the major determinant of metabolic fuel selection at HA, as well as at SL.

Effects of hypoxia and low temperature on substrate fluxes in fish: plasma metabolite concentrations are misleading

Oxygen levels and temperature can fluctuate rapidly in aquatic environments. Ever though the effects of environmental stresses on fish metabolism have been studied extensively, information on fue kinetics is extremely limited because it relies almost exclusively on changes in substrate concentrations. The turnover rate of nonesterified fatty acids (NEFA) has never been measured in fish. Therefore, our goal was to quantify glucose and NEFA fluxes in rainbow trout acutely exposed to severe hypoxia (25% O2 saturation) or low temperature (6 degrees C for fish acclimated to 15 degrees C) by performing continuous infusions of 6-[3H]glucose and 1-[14C]palmitate in vivo. Results show that hypoxia causes a 53% decrease in NEFA turnover rate, together with a transient increase in hepatic glucose production, whereas a rapid drop in temperature induces equivalent declines in glucose, NEFA, and oxygen fluxes [temperature coefficient approximately equal to 2]. More importantly, kinetic changes in glucose and NEFA fluxes are not accompanied by interpretable changes in the plasma concentrations of these metabolites. Thus using concentration changes to draw conclusions about fluxes must be avoided.

Glucose kinetics of the Virginia opossum: possible implications for predicting glucose turnover in mammals

Primed continuous infusions of 6-3H-glucose, respirometry and measurements of nitrogen excretion were carried out in adult Virginia opossums (Didelphis virginiana). Our goals were to determine resting glucose turnover rate, to establish the relative importance of this oxidative fuel in the energy budget of this species, to assess whether metabolic rate is a better predictor of glucose turnover rate than body mass and to demonstrate that glucose kinetics can be measured in the opossum for future use of this animal model in studies of mammalian glucoregulation. Results show that the resting glucose turnover rate of opossums averages 17.5 +/- 0.9 mumol/kg.min (n = 9), that 31% of total glucose flux is oxidized and that glucose oxidation represents 9% of their metabolic rate. An allometric equation predicting glucose turnover rate from body mass for placental mammals overestimates the measured turnover rate of this marsupial by 30%, suggesting that turnover rate is better predicted from metabolic rate than from body mass. Finally, this study demonstrates that the Virginia opossum is a convenient model to study glucose metabolism in vivo, and we propose that the very rapid aging characteristics of this species should be exploited to investigate the effects of aging on glucose homeostasis.

Evolution of the hemagglutinin gene of influenza B virus was driven by both positive and negative selection pressures

Nucleotide sequences of the hemagglutinin (HA) gene of twelve influenza B strains and their deduced amino acid sequences were extracted from the GenBank and compared to those of early isolates. Separate analyses of nonsynonymous and synonymous substitutions for the HA1 and HA2 regions individually indicate that the percentage of nonsynonymous substitutions in the HA1 ranges from 44.4-56.0% but in the HA2 from 0.0-6.5%. The results suggest that positive selection as well as negative selection played a role in the evolution of the influenza B HA gene with the former acting on the HA1 and the latter on the HA2.

Reliability of continuous tracer infusion for measuring glucose turnover rate in rainbow trout

Glucose plays a fundamental role in mammalian energetics but its contribution as a metabolic fuel is not well established for fish; the accurate in vivo measurement of glucose flux is essential to determine the importance of this substrate in the energy budget of teleosts. Therefore, the goal of the present study was to verify the reliability of the continuous tracer infusion method for estimating glucose turnover rate in rainbow trout Oncorhynchus mykiss. Our secondary goals were to determine whether glucose flux can be estimated more accurately from plasma or from whole-blood samples, and to obtain an estimate of renal glucose production. Continuous infusions of [6-3H]glucose were performed in hepatectomized and intact animals. In some hepatectomized individuals, liver glucose production was replaced by a pump infusing unlabelled glucose at a known rate. Renal glucose production was measured in hepatectomized fish where liver glucose production was not replaced, and it averaged 1.1&plusmn;0.1&micro;molkg-1min-1 (mean &plusmn; s.e.m., N=5). Results show that glucose turnover rate is quantified accurately by continuous tracer infusion and that glucose flux can be estimated equally well from plasma (error of -0.7&plusmn;4.9%) and from whole-blood (error of -5.7&plusmn;2.9%) samples (means &plusmn; s.e.m., N=7). This study provides the first experimental validation of continuous tracer infusion in fish, and shows that this method could become a powerful tool to investigate hormonal regulation of glucose metabolism in live teleosts.