Alpha, beta and gamma motoneurons: functional diversity in the motor system's final pathway

Since their discovery in the late 19th century our conception of motoneurons has steadily evolved. Motoneurons share the same general function: they drive the contraction of muscle fibers and are the final common pathway, i.e., the seat of convergence of all the central and peripheral pathways involved in motricity. However, motoneurons innervate different types of muscular targets. Ordinary muscle fibers are subdivided into three main subtypes according to their structural and mechanical properties. Intrafusal muscle fibers located within spindles can elicit either a dynamic, or a static, action on the spindle sensory endings. No less than seven categories of motoneurons have thereby been identified on the basis of their innervation pattern. This functional diversity has hinted at a similar diversity in the inputs each motoneuron receives, as well as in the electrical, or cellular, properties of the motoneurons that match the properties of their muscle targets. The notion of the diverse properties of motoneurons has been well established by the work of many prominent neuroscientists. But in today's scientific literature, it tends to fade and motoneurons are often thought of as a homogenous group, which develop from a given population of precursor cells, and which express a common set of molecules. We first present here the historical milestones that led to the recognition of the functional diversity of motoneurons. We then review how the intrinsic electrical properties of motoneurons are precisely tuned in each category of motoneurons in order to produce an output that is adapted to the contractile properties of their specific targets.

P4-09-10: Assessment of Circulating Immune Parameters in Patients with Metastatic Breast Cancer Improves Survival Prediction

Background

Prediction of survival for metastatic breast cancer (MBC) patients (pts) remains a major clinical challenge. Most studies proposed prognostic scores based on clinical criteria that are often subjective. We already demonstrated that low lymphocyte count is a prognostic factor in various pts populations, and we recently showed that low CD4 lymphocyte count is a prognostic factor for overall survival (OS) in MBC pts. In this study, we evaluate the plasma levels of various cytokines and chemokines to improve our immune-based prognostic model.

Methods: The first cohort (A) consisted of 39 pts with MBC treated with first line chemotherapy between Sep. 04 and Oct. 07. The second cohort (B) consisted of 114 pts with MBC who relapsed after at least one line of chemotherapy between Dec. 2000 and Nov. 05 and who received further chemotherapy. In the cohort A the blood samples were drawn before administration of any chemotherapy. In the cohort B the samples were drawn after white blood cell recovery. Fresh cells have been used for extensive phenotypic analyses. Plasma cytokines levels have been measured using commercially available Luminex-based multiplex kits. Cytokines were clustered into 3 groups based on biological pathways, group 1: Th1 response and T-cell proliferation (IL-2, IL-7, IL-15, IFNγ, IL-12p40, IFNa2, GM-CSF); group 2: Th2 response (IL-10, IL-13, CCL22), and group 3: inflammatory response (IL-1b, IL6, IL-17, TNFα).

Results: In the cohortA: CD4+ T cell levels <450/μL were associated with worse OS (HR=2.46 [CI95%=1.21−5.01), p=0.013). In the cohort B, 48% of pts had received one previous line of chemotherapy; 52% had received more than one. CD4+ T cell levels <450/μL were also associated with worse OS (HR=1.70 [CI95%=1.04−2.78], p=0.036). Analyzing cytokines by clusters, elevation in group 1 (Th1 response) was associated with poor OS for both cohorts A (HR=1.055 [CI95%=1.002−1.111), p=0.041) and B (HR=1.12 [CI95%=1.01−1.24), p=0.032). Conversely, the group 2 (Th2 response) was not associated with OS for both cohorts. For the group 3 (inflammatory response), the increase of these cytokines values was a prognostic factor of OS only for the cohort B (HR=1.10 [CI95%=1.02−1.18), p=0.009). In multivariate analysis: in the cohort A, CD4+ T cell levels <450/μL (HR=2.45 [CI95%=1.20−5.03), p=0.014) and group 1 of cytokines (HR=1.055 [CI95%=1.004−1.109), p=0.034) remains independent prognostic factors; in the cohort B, poor Performance Status (HR=3.10 [CI95%=1.99−4.86), p<0.0001) and group 3 of cytokines (HR=1.09 [CI95%=1.01−1.17), p=0.020) were shown to be independent prognostic factors.

Conclusions: Combination of PS and biological covariates such as lymphocyte CD4+ count or cluster of cytokines is an effective strategy to predict survival of pts with MBC receiving first-line chemotherapy or subsequent lines. The validation of our immune-based prognostic score (combining cytokine levels and immune cell phenotypes) will be initiated in a prospective study.

Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P4-09-10.

P2-12-10: Low TCR Diversity (Divpenia) Is a Prognosis Factor of Overall Survival in Metastatic Breast Cancer

Background: We already showed that lymphopenia (<1000 lymphocytes/μl) or CD4+ T cell lymphopenia (<450/μl) detected before initiation of chemotherapy are prognostic factors for toxicity and death for metastatic breast cancer (MBC) patients. The goal of the present study was to identify the characteristics of the T cells in these lymphopenic patients. TCR diversity was investigated and tested as a prognostic factor for overall survival (OS).

Patients and methods: The ImmunTraCkeR® assay (ImmunID, Grenoble, France), which analyzes through semi quantitative multiplex-PCR the V-D-J combinatorial diversity of TCR-beta chain (TRB), was used to investigate diversity of T cell repertoire on cryopreserved blood samples from a retrospective cohort of MBC patients before chemotherapy administration (n=66). Univariate and multivariate analysis were performed. We then validated our score on a prospective cohort (n=67) using the same eligibility criteria (MBC patients before first line chemotherapy administration).

Results: Using a 33% cutoff for divpenia in our retrospective cohort (T cell diversity below 33%) (average diversity for healthy people is 70%), divpenia was associated with a median OS of 10 months vs 22 months for patients with diversity >33% (logrank p value=0.04). The NDL® score (Numeration Diversity Lymphocytes representation) that combines lymphocyte numeration with TRB diversity, demonstrated that lympho-divpenia (T cell diversity below 33% and lymphopenia below lGiga/L) was associated with a poor OS compared to patients with either lymphocyte <1000/μL & diversity >33% or lymphocyte >1000/μL & diversity <33% or both lymphocyte >1000/μL and diversity >33% (p=0.015). In multivariate analysis, including performance status (PS), hemoglobin level, polynuclear neutrophil count (PNN), age, and liver metastasis, NDL® score was identified as an independent prognostic factor for OS. In our prospective validation cohort, NDL® score was also identified as a prognostic factors for OS (p=0,007), as well as lymphopenia (<1000/μL) (p=0,0003), CD4+ lymphopenia (<450/μL) (p=0,04), menopausal status (p=0,02), hormonal receptor status (estrogen receptor p=0.02; progesterone receptor p=0.002) and lung metastasis (p=0,009). In multivariate analysis, hemoglobin level was the only independent prognostic factor in this cohort.

Conclusion: We showed that Divpenia and NDL® score are prognostic factors for OS in MBC patients. In order to confirm these results, a prospective clinical trial is ongoing on a larger cohort of MBC and lung cancer patients.

Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P2-12-10.

The response of CR-39 nuclear track detector to 1-9 MeV protons

The response of CR-39 nuclear track detector (TasTrak(®)) to protons in the energy range of 0.92-9.28 MeV has been studied. Previous studies of the CR-39 response to protons have been extended by examining the piece-to-piece variability in addition to the effects of etch time and etchant temperature; it is shown that the shape of the CR-39 response curve to protons can vary from piece-to-piece. Effects due to the age of CR-39 have also been studied using 5.5 MeV alpha particles over a 5-year period. Track diameters were found to degrade with the age of the CR-39 itself rather than the age of the tracks, consistent with previous studies utilizing different CR-39 over shorter time periods.

Increasing the energy dynamic range of solid-state nuclear track detectors using multiple surfaces

Solid-state nuclear track detectors, such as CR-39, are widely used in physics and in many inertial confinement fusion (ICF) experiments. In the ICF experiments, the particles of interest, such as D(3)He-protons, have ranges of order of the detector thickness. In this case, the dynamic range of the detector can be extended by recording data on both the front and back sides of the detector. Higher energy particles which are undetectable on the front surface can then be measured on the back of the detector. Studies of track formation under the conditions on the front and back of the detector reveal significant differences. Distinct front and back energy calibrations of CR-39 are therefore necessary and are presented for protons. Utilizing multiple surfaces with additional calibrations can extend the range of detectable energies on a single piece of CR-39 by up to 7-8 MeV. The track formation process is explored with a Monte Carlo code, which shows that the track formation difference between front and back is due to the non-uniform ion energy deposition in matter.

Improved phylogenomic taxon sampling noticeably affects nonbilaterian relationships

Despite expanding data sets and advances in phylogenomic methods, deep-level metazoan relationships remain highly controversial. Recent phylogenomic analyses depart from classical concepts in recovering ctenophores as the earliest branching metazoan taxon and propose a sister-group relationship between sponges and cnidarians (e.g., Dunn CW, Hejnol A, Matus DQ, et al. (18 co-authors). 2008. Broad phylogenomic sampling improves resolution of the animal tree of life. Nature 452:745–749). Here, we argue that these results are artifacts stemming from insufficient taxon sampling and long-branch attraction (LBA). By increasing taxon sampling from previously unsampled nonbilaterians and using an identical gene set to that reported by Dunn et al., we recover monophyletic Porifera as the sister group to all other Metazoa. This suggests that the basal position of the fast-evolving Ctenophora proposed by Dunn et al. was due to LBA and that broad taxon sampling is of fundamental importance to metazoan phylogenomic analyses. Additionally, saturation in the Dunn et al. character set is comparatively high, possibly contributing to the poor support for some nonbilaterian nodes.

Sponge paraphyly and the origin of Metazoa

In order to allow critical evaluation of the interrelationships between the three sponge classes, and to resolve the question of mono- or paraphyly of sponges (Porifera), we used the polymerase chain reaction (PCR) to amplify almost the entire nucleic acid sequence of the 18S rDNA from several hexactinellid, demosponge and calcareous sponge species. The amplification products were cloned, sequenced and then aligned with previously reported sequences from other sponges and nonsponge metazoans and variously distant outgroups, and trees were constructed using both neighbour-joining and maximum parsimony methods. Our results suggest that sponges are paraphyletic, the Calcarea being more related to monophyletic Eumetazoa than to the siliceous sponges (Demospongiae, Hexactinellida). These results have important implications for our understanding of metazoan origins, because they suggest that the common ancestor of Metazoa was a sponge. They also have consequences for basal metazoan classification, implying that the phylum Porifera should be abandoned. Our results support the upgrading of the calcareous sponge class to the phylum level.

Monoenergetic-proton-radiography measurements of implosion dynamics in direct-drive inertial-confinement fusion

Time-gated, monoenergetic radiography with 15-MeV protons provides unique measurements of implosion dynamics in direct-drive inertial-confinement fusion. Images obtained during acceleration, coasting, deceleration, and stagnation display a comprehensive picture of spherical implosions. Critical information inferred from such images, hitherto unavailable, characterizes the spatial structure and temporal evolution of self-generated fields and plasma areal density. Results include the first observation of a radial electric field inside the imploding capsule. It is initially directed inward (at approximately 10(9) V/m), eventually reverses direction ( approximately 10(8) V/m), and is the probable consequence of the evolution of the electron pressure gradient.

[Epidemiological study of lung cancer in Portugal (2000/2002)]

Lung cancer is the most common form of cancer death in the world. Five-year survival is about 15%, without any change to this picture envisaged. It is the 3rd most prevalent type of cancer in Portugal and the primary cause of cancer death. 85% of lung cancer cases are attributable to smoking. One study performed in Portugal for 3 years (2000/2002) by the Lung Oncology Work Committee of the Portuguese Society of Pulmonology in 22 Hospitals showed that of a total of 4396 patients with lung cancer, 81.8% were male and 18.2% were female, with a mean age of 64.49 +/- 11.28 years. About 70% of patients were smokers or former smokers, with 50.3% of patients presenting with performance status (Zubrod) 1. Histologically, 37.5% were adenocarcinoma, followed by squamous carcinoma in 30.5% of cases, and small cell lung cancer in 12.5%; neuroendocrine carcinoma presented in 1.4% of cases; non small cell lung cancer in 10.5%; mixed carcinoma in 0.7%; large cell carcinoma in 2.3%; and others/not specified in 4.6% of cases. Staging (known in 4097 patients), showed 113 patients in stage IA (2.8%)and 250 patients in stage IB (6.1%); only 0.8% in stage IIA and 4.5% in stage IIB; 9.1% in stage IIIA and 29.9% in stage IIIB; 46.9% were already in stage IV by the time of diagnosis. The first therapeutic option was known in 3855 patients. Surgery was performed in 8.2% and 21.8% of cases were treated with combined therapies (surgery and chemotherapy or radiotherapy, or combination of chemotherapy and radiotherapy); chemotherapy alone was first choice in 43.7% of patients and in 20.3% only best support therapy was chosen.

The afterhyperpolarization conductance exerts the same control over the gain and variability of motoneurone firing in anaesthetized cats

Does the afterhyperpolarization current control the gain and discharge variability of motoneurones according to the same law? We investigated this issue in lumbar motoneurones of anaesthetized cats. Using dynamic clamp, we measured the conductance, time constant and driving force of the AHP current in a sample of motoneurones and studied how the gain was correlated to these quantities. To study the action of the AHP on the discharge variability and to compare it to its action on the gain, we injected an artificial AHP-like current in motoneurones. This increased the natural AHP. In three motoneurones, we abolished most of the natural AHP with the calcium chelator BAPTA to investigate the condition where the discharge was essentially controlled by the artificial AHP. Our results demonstrate that both the gain and the coefficient of variation of the firing rate are inversely proportional to the magnitude and to the time constant of the artificial AHP conductance. This indicates that the AHP exerts the same control over the gain and the variability. This mechanism ensures that the variability of the discharge is modulated with the gain. This guarantees a great regularity of the discharge when the motoneurone is in a low excitability state and hence good control of the force produced.

How much afterhyperpolarization conductance is recruited by an action potential? A dynamic-clamp study in cat lumbar motoneurons

We accurately measured the conductance responsible for the afterhyperpolarization (medium AHP) that follows a single spike in spinal motoneurons of anesthetized cats. This was done by using the dynamic-clamp method. We injected an artificial current in the neurons that increased the AHP amplitude, and we made use of the fact that the intensity of the natural AHP current at the trough of the voltage trajectory was related linearly to the AHP amplitude. We determined at the same time the conductance and the reversal potential of the AHP current. This new method was validated by a simple theoretical model incorporating AHP and hyperpolarization-activated (Ih) currents and could be applied when the decay time constant of the AHP conductance was at least five times shorter than the estimated Ih activation time. This condition was fulfilled in 33 of 44 motoneurons. The AHP conductance varied from 0.3 to 1.4 microS in both slow- and fast-type motoneurons, which was approximately the same range as the input conductance of the entire population. However, AHP and input conductances were not correlated. The larger AHP in slow-type motoneurons was mainly attributable to their smaller input conductance compared with fast motoneurons. The likeness of the AHP conductance in both types of motoneurons is in sharp contrast to differences in AHP decay time and explains why slow- and fast-type motoneurons have similar gain.

Phylogeny and evolution of calcareous sponges

The most recent advances concerning the phylogeny and evolution of calcareous sponges (Calcarea or Calcispongia) are reviewed here, in the light of the history of taxonomy of the group and conceptions about its evolution, starting from Haeckel's works at the end of the 19th century. Calcisponge phylogeny has recently started to be addressed using modern tools of phylogenetic reconstruction: cladistic analysis of morphological characters and molecular phylogeny (so far using 18S and 28S rDNA sequences). The monophyly of calcareous sponges is strongly supported in these works, as is their subdivision into two clades, Calcinea (whose proposed synapomorphy is the basal position of nuclei in choanocytes, with no relation to the flagella) and Calcaronea (whose possible synapomorphy is the formation of the amphiblastula larva through the original process of eversion of the stomoblastula). While the molecular phylogeny of Calcinea is still in its infancy because of insufficient taxonomic sampling, several lines are emerging for the phylogeny of Calcaronea, and these are in strong disagreement with the classification issued from the "traditional" morphological approach. Phylogenetic hypotheses also permit the reconstruction of morphological character evolution, which appears complex and subject to a high level of homoplasy.

Homeobox gene diversification in the calcareous sponge, Sycon raphanus

Knowledge of the developmental mechanisms in living basal metazoan phyla is crucial for understanding the genetic bases of morphological evolution in early animal history. We looked for homeobox genes in the calcareous sponge, Sycon raphanus, using the polymerase chain reaction. Partial sequences of eight homeoboxes were recovered, five of which are assignable to the NK-2 class of homeoboxes. The three remaining sequences are related members of a new class of homeoboxes, the Sycox class, showing limited similarity to bilaterian Lbx, Hlx, HEX, En, and Cad classes. Among the five NK-2 class homeoboxes are four closely related sequences occupying a divergent position within the class, the remaining one on the contrary showing high sequence similarity with members of the NK-2 family, a particular subgroup within the NK-2 class, previously known only from the Bilateria. This suggests that diversification of the NK-2 class occurred early in metazoan history. Altogether, the results reveal an unexpected diversification of homeobox genes in S. raphanus.

The comparison of beta-thymosin homologues among metazoa supports an arthropod-nematode clade

The definition of an Ecdysozoa clade among the protostomians, including all phyla with a regularly molted alpha-chitin-rich cuticle, has been one of the most provocative hypotheses to arise from recent investigations on animal phylogeny. Here we present evidence in favor of an arthropod-nematode clade, from the comparison of beta-thymosin homologues among the Metazoa. Arthropods and nematodes share the absence of the highly conserved beta-thymosin form found in all other documented bilaterian phyla as well as sponges, and the possession of a very unusual, internally triplicated homologue of the beta-thymosin protein, unknown in other phyla. We argue that such discrete molecular character is phylogenetically very powerful and provides strong evidence for the monophyly of an arthropod-nematode clade.

Requirement of endogenous stem cell factor and granulocyte-colony-stimulating factor for IL-17-mediated granulopoiesis

IL-17 is a novel, CD4+ T cell-restricted cytokine. In vivo, it stimulates hematopoiesis and causes neutrophilia consisting of mature granulocytes. In this study, we show that IL-17-mediated granulopoiesis requires G-CSF release and the presence or induction of the transmembrane form of stem cell factor (SCF) for optimal granulopoiesis. However, IL-17 also protects mice from G-CSF neutralization-induced neutropenia. G-CSF neutralization completely reversed IL-17-induced BM progenitor expansion, whereas splenic CFU-GM/CFU-granulocyte-erythrocyte-megakaryocyte-monocyte was only reduced by 50% in both Sl/Sld and littermate control mice. Thus, there remained a significant SCF/G-CSF-independent effect of IL-17 on splenic granulopoiesis, resulting in a preservation of mature circulating granulocytes. IL-17 is a cytokine that potentially interconnects lymphocytic and myeloid host defense and may have potential for therapeutic development.

Cyclosporin A induces an atypical heat shock response

Cyclosporin A is a widely used immunosuppressive drug having toxic side effects, in particular on kidneys and liver, as a result of its action on different molecular targets. Here we demonstrate that low doses of CsA are able to induce the expression of the heat shock protein HSP27 and its hyperphosphorylation. It also activates the two heat shock transcription factors, HSF1 and HSF2. Since these factors have been shown to be activated by proteasome inhibition, we tested the hypothesis that the inhibitory action of CsA on the proteasome might be responsible for the activation of HSFs and the subsequent expression of HSP27. The increase in multiubiquitinated proteins as well as the stabilization of p53 following CsA addition argues in favor of this hypothesis. The kidney BSC-1 cells are highly responsive to the addition of CsA: the possible link between HSP27 induction and hyperphosphorylation and nephrotoxicity is discussed.

Horizontal transfer of genetic material among Saccharomyces yeasts

The genus Saccharomyces consists of several species divided into the sensu stricto and the sensu lato groups. The genomes of these species differ in the number and organization of nuclear chromosomes and in the size and organization of mitochondrial DNA (mtDNA). In the present experiments we examined whether these yeasts can exchange DNA and thereby create novel combinations of genetic material. Several putative haploid, heterothallic yeast strains were isolated from different Saccharomyces species. All of these strains secreted an a- or alpha-like pheromone recognized by S. cerevisiae tester strains. When interspecific crosses were performed by mass mating between these strains, hybrid zygotes were often detected. In general, the less related the two parental species were, the fewer hybrids they gave. For some crosses, viable hybrids could be obtained by selection on minimal medium and their nuclear chromosomes and mtDNA were examined. Often the frequency of viable hybrids was very low. Sometimes putative hybrids could not be propagated at all. In the case of sensu stricto yeasts, stable viable hybrids were obtained. These contained both parental sets of chromosomes but mtDNA from only one parent. In the case of sensu lato hybrids, during genetic stabilization one set of the parental chromosomes was partially or completely lost and the stable mtDNA originated from the same parent as the majority of the nuclear chromosomes. Apparently, the interspecific hybrid genome was genetically more or less stable when the genetic material originated from phylogenetically relatively closely related parents; both sets of nuclear genetic material could be transmitted and preserved in the progeny. In the case of more distantly related parents, only one parental set, and perhaps some fragments of the other one, could be found in genetically stabilized hybrid lines. The results obtained indicate that Saccharomyces yeasts have a potential to exchange genetic material. If Saccharomyces isolates could mate freely in nature, horizontal transfer of genetic material could have occurred during the evolution of modern yeast species.

Genomic structure and chromosomal localization of the mouse Hsf2 gene and promoter sequences

The mouse heat shock factor 2 (HSF2) cDNA was previously cloned by homology to HSF1, the heat shock factor involved in the cellular response to stress [Sarge, K.D., Zimarino, V., Holm, K., Wu, C., Morimoto, R.I., Cloning and characterization of two mouse heat shock factors with distinct inducible and constitutive DNA-binding ability. Genes Dev. 5 (1991) 1902-1911]. HSF2 is active in restricted cell types during pre- and post-implantation stages of development, and only in male germ cells of adult mice. However, the function of this factor remains elusive. We report here the cloning of the mouse Hsf2 gene and its genomic structure. We show that the gene is composed of 13 exons of variable sizes spanning at least 43kb in the genome. The transcription start site has been determined, and upstream sequences with promoter activity have been identified by their ability to direct the expression of a luciferase reporter gene in transfected cells. A preliminary analysis of the proximal promoter sequence determined that the TATA box is absent, but that a GC-rich region with several potential binding sites for transcription factors is present. The gene has been mapped to mouse chromosome 10 by in-situ hybridization on metaphase chromosomes.

Contribution of reactive oxygen and nitrogen species to particulate-induced lung injury

Recently, a second pathway for the generation of potential oxidants with the reactivity of the hydroxyl radical without the need for metal catalysis has been described. In response to various inflammatory stimuli, lung endothelial, alveolar, and airway epithelial cells, as well as activated alveolar macrophages, produce both nitric oxide (.NO) and superoxide anion radicals (O2.-). .NO regulates pulmonary vascular and airway tone and plays an important role in lung host defense against various bacteria. However, .NO may be cytotoxic by inhibiting critical enzymes such as mitochondrial aconitase and ribonucleotide reductase, by S-nitrosolation of thiol groups, or by binding to their iron-sulfur centers. In addition, .NO reacts with O2.- at a near diffusion-limited rate to form the strong oxidant peroxynitrite (ONOO-), which can nitrate and oxidize key amino acids in various lung proteins such as surfactant protein A, and inhibit their functions. The presence of ONOO- in the lungs of patients with acute respiratory distress syndrome has been demonstrated by measuring levels of nitrotyrosine, the stable product of tyrosine nitration. Various studies have shown that inhalation or intratracheal instillation of various respirable mineral dusts or asbestos fibers increased levels of inducible nitric oxide synthase mRNA. In this presentation, we review the evidence for the upregulation of .NO in the lungs of animals exposed to mineral particulates and assess the contribution of reactive nitrogen species in the pathogenesis of the resultant lung injury.