Carbon isotope ratios of respired CO2 from castor bean, corn, peanut, pea, radish, squash, sunflower and wheat seedlings

During the first month after germination peanut and sunflowerseedlings exhibit a significant shift in the ¹³C/¹²C ratiosof respired CO₂ indicating thatcarbohydrate gives way to lipidas the respiratory substrate. Other species (castor bean, corn,pea,radish, squash and wheat) show no change in the ¹³C/¹²C ratio (Received March 9, 1971; )     

Evolutionary context for understanding and manipulating plant responses to past, present and future atmospheric [CO2

Variation in atmospheric [CO(2)] is a prominent feature of the environmental history over which vascular plants have evolved. Periods of falling and low [CO(2)] in the palaeo-record appear to have created selective pressure for important adaptations in modern plants. Today, rising [CO(2)] is a key component of anthropogenic global environmental change that will impact plants and the ecosystem goods and services they deliver. Currently, there is limited evidence that natural plant populations have evolved in response to contemporary increases in [CO(2)] in ways that increase plant productivity or fitness, and no evidence for incidental breeding of crop varieties to achieve greater yield enhancement from rising [CO(2)]. Evolutionary responses to elevated [CO(2)] have been studied by applying selection in controlled environments, quantitative genetics and trait-based approaches. Findings to date suggest that adaptive changes in plant traits in response to future [CO(2)] will not be consistently observed across species or environments and will not be large in magnitude compared with physiological and ecological responses to future [CO(2)]. This lack of evidence for strong evolutionary effects of elevated [CO(2)] is surprising, given the large effects of elevated [CO(2)] on plant phenotypes. New studies under more stressful, complex environmental conditions associated with climate change may revise this view. Efforts are underway to engineer plants to: (i) overcome the limitations to photosynthesis from today's [CO(2)] and (ii) benefit maximally from future, greater [CO(2)]. Targets range in scale from manipulating the function of a single enzyme (e.g. Rubisco) to adding metabolic pathways from bacteria as well as engineering the structural and functional components necessary for C(4) photosynthesis into C(3) leaves. Successfully improving plant performance will depend on combining the knowledge of the evolutionary context, cellular basis and physiological integration of plant responses to varying [CO(2)].     

Coupled, but not uncoupled, fluxes in a neuronal glutamate transporter can be activated by lithium ions

In the central nervous system a family of related (Na(+)-K(+))-coupled glutamate transporters remove the transmitter from the cleft and prevent its neurotoxic actions. In addition to this coupled uptake, these transporters also mediate a sodium- and glutamate-dependent uncoupled anion conductance. Most models assume that the initial steps for both processes are the same, leading to the anticipation that both may exhibit a similar requirement for cations. In this study we have tested this idea in the neuronal glutamate transporter EAAC-1. We report that in this transporter lithium can replace sodium in the coupled uptake. Strikingly, the glutamate-dependent gating of the uncoupled conductance mediated by EAAC-1 has a strict requirement for sodium; lithium cannot substitute for it. Moreover, we describe two mutants, T370S and G410S, in which the cation selectivity of the two processes is affected differently. In both mutants sodium, but not lithium, can support coupled transport. On the other hand, the sodium selectivity of the gated anion conductance in oocytes expressing the mutant transporters is not affected. Our observations indicate that although both the coupled and the uncoupled fluxes are sodium-dependent, the conformation gating the anion conductance is different from that during substrate translocation.     

Firefly luciferase, synthesized to very high levels in caterpillars infected with a recombinant baculovirus, can also be used as an efficient reporter enzyme in vivo

Trichoplusia ni and Spodoptera littoralis larvae were infected with a recombinant AcNPV, having the viral polyhedrin gene replaced with the cDNA encoding firefly luciferase. Both S. littoralis and T. ni synthesized very high levels of luciferase representing greater than or equal to 25% and greater than or equal to 15%, respectively of the total Coomassie blue stainable protein. Luciferase was apparently not secreted into the hemolymph but was contained within the body tissue. Expression in S. littoralis larvae suggests that luciferase can be an excellent reporter enzyme to study virus infection, dissemination and expression in different tissues, host range determination, insect physiology and also to monitor the release of recombinant virus in the environment when used as a biocide.     

Quin2-induced metaphase arrest in stamen hair cells can be reversed by 1,2-dioctanoylglycerol but not by 1,3-dioctanoylglycerol

Elicitor molecules of the polyphosphoinositide cycle, inositol 1,4,5-trisphosphate (InsP3) and 1,2-diacylglycerol (1,2-DAG) play roles in the entry of calcium into the cytosol and in the elevation of protein kinase C activity, respectively. We have treated stamen hair cells of the spiderwort plant, Tradescantia virginiana, with a solution of quin2 (50 microM) or its acetoxymethyl ester, quin2-AM (50 microM) and have retarded the normally predictable rate of progression through metaphase. Metaphase arrest persists for longer than 80 min after treatment with this Ca2+-chelator, and, shortly thereafter, the cells revert to interphase without dividing. Reversal of metaphase arrest results from treatments with calcium chloride (100 microM) after 5 to 8 min or with 1,2-DAG (i.e., 60 micrograms/ml 1,2-dioctanoylglycerol) after 7 to 11 min. In control experiments, metaphase arrest could not be reversed by treatment with either magnesium sulfate or 1,3-dioctanoylglycerol. Anaphase onset was observed in these control cells after post-treatment with calcium chloride (after 4-9 min) or with 1,2-dioctanoylglycerol (after 7-13 min). The treatment of stamen hair cells in very early prophase with H-7, (i.e., 1-(5-isoquinolinesulfonyl)-2-methylpiperazine dihydrochloride), a potent protein kinase C inhibitor, extends the duration of metaphase significantly. Neither H-8 nor HA-1004, less active protein kinase C inhibitors in this class of molecules, alter the duration of metaphase to a significant extent. These results suggest that in cells arrested in metaphyase by quin2, calcium translocation plays a role in the sequence of events which culminate in anaphase.(ABSTRACT TRUNCATED AT 250 WORDS)     

Raphe magnus nucleus is involved in ventilatory but not hypothermic response to CO2.

There is evidence that serotonin [5-hydroxytryptamine (5-HT)] is involved in the physiological responses to hypercapnia. Serotonergic neurons represent the major cell type (comprising 15-20% of the neurons) in raphe magnus nucleus (RMg), which is a medullary raphe nucleus. In the present study, we tested the hypothesis 1) that RMg plays a role in the ventilatory and thermal responses to hypercapnia, and 2) that RMg serotonergic neurons are involved in these responses. To this end, we microinjected 1) ibotenic acid to promote nonspecific lesioning of neurons in the RMg, or 2) anti-SERT-SAP (an immunotoxin that utilizes a monoclonal antibody to the third extracellular domain of the serotonin reuptake transporter) to specifically kill the serotonergic neurons in the RMg. Hypercapnia caused hyperventilation and hypothermia in all groups. RMg nonspecific lesions elicited a significant reduction of the ventilatory response to hypercapnia due to lower tidal volume (Vt) and respiratory frequency. Rats submitted to specific killing of RMg serotonergic neurons showed no consistent difference in ventilation during air breathing but had a decreased ventilatory response to CO(2) due to lower Vt. The hypercapnia-induced hypothermia was not affected by specific or nonspecific lesions of RMg serotonergic neurons. These data suggest that RMg serotonergic neurons do not participate in the tonic maintenance of ventilation during air breathing but contribute to the ventilatory response to CO(2). Ultimately, this nucleus may not be involved in the thermal responses to CO(2).     

The frameshift mutation in Nod2 results in unresponsiveness not only to Nod2- but also Nod1-activating peptidoglycan agonists

NOD2/CARD15 is the first characterized susceptibility gene in Crohn disease. The Nod2 1007fs (Nod2fs) frameshift mutation is the most prevalent in Crohn disease patients. Muramyl dipeptide from bacterial peptidoglycan is the minimal motif detected by Nod2 but not by Nod2fs. Here we investigated the response of human peripheral blood mononuclear cells (PBMCs) from Crohn disease patients not only to muramyl dipeptide but also to several other muramyl peptides. Most unexpectedly, we observed that patients homozygous for the Nod2fs mutation were totally unresponsive to MurNAc-L-Ala-D-Glu-meso-diaminopimelic acid (DAP) (M-Tri(DAP)), the specific agonist of Nod1, and to Gram-negative bacterial peptidoglycan. In contrast, PBMCs from a patient homozygous for the Nod2 R702W mutation, also associated with Crohn disease, displayed normal response to Gram-negative bacterial peptidoglycan. In addition, the blockage of the Nod1/M-Tri(DAP) pathway could be partially overcome by co-stimulation with the Toll-like receptors agonists lipoteichoic acid or lipopolysaccharide. Investigation into the mechanism of this finding revealed that Nod2fs did not act as a dominant-negative molecule for the Nod1/M-Tri(DAP) pathway, implying that the blockage is dependent upon the expression or activity of other factors. We demonstrated that PBMCs from Nod2fs patients express high levels of the peptidoglycan recognition protein S, a secreted protein known to interact with muramyl peptides. We proposed that through a scavenger function, peptidoglycan recognition protein S may dampen M-Tri(DAP)-dependent responses in Nod2fs patients. Together, our results identified a cross-talk between the Nod1 and Nod2 pathways and suggested that down-regulation of Nod1/M-Tri(DAP) pathway may be associated with Crohn disease.     

Flowering phenology in a species-rich temperate grassland is sensitive to warming but not elevated CO2

* Flowering is a critical stage in plant life cycles, and changes might alter processes at the species, community and ecosystem levels. Therefore, likely flowering-time responses to global change drivers are needed for predictions of global change impacts on natural and managed ecosystems. * Here, the impact of elevated atmospheric CO2 concentration ([CO2]) (550 micromol mol(-1)) and warming (+2 masculineC) is reported on flowering times in a native, species-rich, temperate grassland in Tasmania, Australia in both 2004 and 2005. * Elevated [CO2] did not affect average time of first flowering in either year, only affecting three out of 23 species. Warming reduced time to first flowering by an average of 19.1 d in 2004, acting on most species, but did not significantly alter flowering time in 2005, which might be related to the timing of rainfall. Elevated [CO2] and warming treatments did not interact on flowering time. * These results show elevated [CO2] did not alter average flowering time or duration in this grassland; neither did it alter the response to warming. Therefore, flowering phenology appears insensitive to increasing [CO2] in this ecosystem, although the response to warming varies between years but can be strong.     

Plastid-bearing sea slugs fix CO2 in the light but do not require photosynthesis to survive

Several sacoglossan sea slugs (Plakobranchoidea) feed upon plastids of large unicellular algae. Four species—called long-term retention (LtR) species—are known to sequester ingested plastids within specialized cells of the digestive gland. There, the stolen plastids (kleptoplasts) remain photosynthetically active for several months, during which time LtR species can survive without additional food uptake. Kleptoplast longevity has long been puzzling, because the slugs do not sequester algal nuclei that could support photosystem maintenance. It is widely assumed that the slugs survive starvation by means of kleptoplast photosynthesis, yet direct evidence to support that view is lacking. We show that two LtR plakobranchids, Elysia timida and Plakobranchus ocellatus, incorporate ¹⁴CO₂ into acid-stable products 60- and 64-fold more rapidly in the light than in the dark, respectively. Despite this light-dependent CO₂ fixation ability, light is, surprisingly, not essential for the slugs to survive starvation. LtR animals survived several months of starvation (i) in complete darkness and (ii) in the light in the presence of the photosynthesis inhibitor monolinuron, all while not losing weight faster than the control animals. Contrary to current views, sacoglossan kleptoplasts seem to be slowly digested food reserves, not a source of solar power.     

Murine thyroid follicular epithelial cells can be induced to express class II (Ia) gene products but fail to present antigen in vitro

To determine whether thyroid follicular epithelial cells (TFEC) might be involved in the induction of autoimmune thyroiditis, they were tested for their potential to express Ia antigens, and for their ability to present antigen in vitro. Results showed that Ia antigens, absent on normal TFEC, could be readily induced with interferon gamma, as detected by immunofluorescence. Maximal expression of Ia antigens in over 50% of TFEC was observed after 4 days of culture in the presence of IFN-gamma, and was quantitatively comparable to spleen cells by cytofluorometric analysis. Moreover, primary TFEC in culture secreted thyroglobulin (tg) and interleukin 1. However, TFEC consistently failed to stimulate various populations of T cells. These included lymph node cells sensitized to tg, a T-cell clone specific for azo-benzene-arsonate tyrosine (ABA), and a hybridoma specific for beef insulin. Likewise, Ia-positive TFEC did not stimulate T-cell hybridomas restricted to the class II alloantigen I-Ab, while stimulating a hybridoma specific for the class I alloantigen Kb. T-cell unresponsiveness could not be explained by inhibitory activity of TFEC, released either into the culture supernatant or exerted by cell contact. The data indicate that Ia-positive TFEC failed to serve as class II-restricted antigen-presenting cells (APC) in vitro and thus argue against a primary role for these cells in the inductive phase of thyroiditis.     

Reference ranges for urinary concentrations and ratios of endogenous steroids, which can be used as markers for steroid misuse, in a Caucasian population of athletes

The detection of misuse with naturally occuring steroids is a great challenge for doping control laboratories. Intake of natural anabolic steroids alters the steroid profile. Thus, screening for exogenous use of these steroids can be established by monitoring a range of endogenous steroids, which constitute the steroid profile, and evaluate their concentrations and ratios against reference ranges. Elevated values of the steroid profile constitute an atypical finding after which a confirmatory IRMS procedure is needed to unequivocally establish the exogenous origin of a natural steroid. However, the large inter-individual differences in urinary steroid concentrations and the recent availability of a whole range of natural steroids (e.g. dehydroepiandrosterone and androstenedione) which each exert a different effect on the monitored parameters in doping control complicate the interpretation of the current steroid profile.The screening of an extended steroid profile can provide additional parameters to support the atypical findings and can give specific information upon the steroids which have been administered.The natural concentrations of 29 endogenous steroids and 11 ratios in a predominantly Caucasian population of athletes were determined. The upper reference values at 97.5%, 99% and 99.9% levels were assessed for male (n = 2027) and female (n = 1004) populations. Monitoring minor metabolites and evaluation of concentration ratios with respect to their natural abundances could improve the interpretation of the steroid profile in doping analysis.     

Atmospheric CO2 concentration may directly affect leaf respiration measurement in tobacco,but not respiration itself*

When atmospheric CO₂ concentration increases, various consequences for plant metabolism have been suggested, such as changes in photosynthesis, photorespiration or respiration which can affect growth and carbon sequestration. In addition to long‐term (indirect) effects on respiration, short‐term (direct) effects of CO₂ concentration on the respiration of leaves, shoots and roots are described in the literature. In most cases, respiration is reported to be inhibited by increased CO₂ concentration, but the mechanism(s) are not yet understood. It has been shown previously that, when the respective technical problems and properties of a gas exchange system are fully considered, a short‐term increase in CO₂ (up to 4200 µmol mol^?1) had no effect on respiration of Phaseolus or Populus leaves (Jahnke, Plant, Cell and Environment 24, 1139–1151, 2001). However, in the present study, large (apparent) CO₂ effects were found with mature Nicotiana leaves whereas, in young leaves, the effect was absent. The experimental results clearly show that the observed direct CO₂ effect on dark CO₂ efflux in the mature tobacco leaves was caused by leakage of CO₂ inside the leaves (and the magnitude of the effect was dependent on the size of the leakage). Nicotiana leaves are, in contrast to Phaseolus and Populus leaves (which are heterobaric), characterized by a homobaric anatomy in which intercellular air spaces are not compartmented and provide a continuous system of open pores in the lateral (paradermal) direction of the leaves. Mesophyll porosity increases with leaf development, which explains the differences between young and mature tobacco leaves. When internal leakage was experimentally restricted, the CO₂ inhibition on CO₂ efflux was no longer observed. It is concluded that the measured direct CO₂ effect(s) on leaf CO₂ efflux in the dark are artefactual, and that a true direct CO₂ effect on leaf respiration does not exist.     

Chlamydia trachomatis (L2 serovar) can be bound, ingested and destroyed by differentiated but not by undifferentiated human promyelocyte cell line HL-60

As a model system for analysing interactions between chlamydiae and myeloid cells and their precursors, we have studied binding, ingestion and destruction of Chlamydia trachomatis (L2 serovar) by the human promyelocytic cell line HL-60. HL-60 cells were induced by phorbol myristate acetate (PMA) and dimethyl sulphoxide (DMSO) to differentiate along either the macrophage or the granulocyte pathway, respectively. Using an immunofluorescence assay and electron microscopy, we have shown that induced (differentiated) HL-60 cells, but not uninduced (undifferentiated) HL-60 or other cell lines treated with PMA or DMSO, exhibit increased binding, ingestion and elimination of C. trachomatis; these activities are associated with specific histochemical and antigenic markers of myeloid differentiation. These results suggest that myeloid cells acquire the ability to interact with and kill chlamydiae during cell development.     

High mobility group proteins 1 and 2 are present in simian virus 40 provirions, but not in virions.

Viral particles at the late stages of SV40 morphogenesis were examined for the presence of HMG proteins 1 and 2, by an immunochemical method involving the transfer of proteins from polyacrylamide gels to nitrocellulose membranes. It was found that these proteins are present in SV40 provirions, in which histone H1 is still associated with viral chromatin, but absent in mature SV40 virions.     

Evidence that ICI 118, 551 is a potent, highly Beta 2-selective adrenoceptor antagonist and can be used to characterize Beta-adrenoceptor populations in tissues

pA₂ values for a new ß-adrenoceptor antagonist, ICI 118, 551 (erythro-DL-1(7-methylindan-4-yloxy)-3-isopropylaminobutan-2-o1), have been obtained on intrinsic tone tracheal chain preparations and on spontaneously beating atrial preparations from guinea-pigs. Two different agonists, fenoterol (ß₂-selective) and noradrenaline (ß₁-selective) were used. The slopes of the Schild plots were not significantly different from 1.0. The antagonist was very potent (pA₂ on trachea, fenoterol as agonist, was 8.69) and also highly ß₂-selective (pA₂ on atria, noradrenaline as agonist, was only 6.96). On guinea-pig trachea (which contains ß₁- and ß₂-adrenoceptors) the potency was 44 times higher when fenoterol was the agonist than when noradrenaline was the agonist. On guinea-pig atria (which contains only ß₁-adrenoceptors) the pA₂ value was the same whichever agonist was used. Thus ICI 118, 551 has been shown to be potent and the most ß₂-selective antagonist so far studied in our laboratory. In experiments carried out with selective agonists ICI 118, 551 distinguished clearly between tissues with a mixed ß-adrenoceptor population (different pA₂ values) and those with a homogeneous population (single pA₂ value). Therefore, ICI 118, 551 is a valuable addition to the group of ß₂-selective adrenoceptor antagonists.