Cytotoxicity of Mn-based photoCORMs of ethynyl-α-diimine ligands against different cancer cell lines: The key role of CO-depleted metal fragments

A series of tricarbonyl manganese complexes bearing 4-ethynyl-2,2'-bipyridine and 5-ethynyl-1,10-phenanthroline α-diimine ligands were synthetized, characterized and conjugated to vitamin B₁₂, previously used as a vector for drug delivery, to take advantage of its water solubility and specificity toward cancer cells. The compounds act as photoactivatable carbon monoxide-releasing molecules rapidly liberating on average ca. 2.3 equivalents of CO upon photo-irradiation. Complexes and conjugates were tested for their anticancer effects, both in the dark and following photo-activation, against breast cancer MCF-7, lung carcinoma A549 and colon adenocarcinoma HT29 cell lines as well as immortalized human bronchial epithelial cells 16HBE14o- as the non-carcinogenic control. Our results indicate that the light-induced cytotoxicity these molecules can be attributed to both their released CO and to their CO-depleted metal fragments including liberated ligands.

Antiplasmodial Activity and In Vivo Bio-Distribution of Chloroquine Molecules Released with a 4-(4-Ethynylphenyl)-Triazole Moiety from Organometallo-Cobalamins

We have explored the possibility of using organometallic derivatives of cobalamin as a scaffold for the delivery of the same antimalarial drug to both erythro- and hepatocytes. This hybrid molecule approach, intended as a possible tool for the development of multi-stage antimalarial agents, pivots on the preparation of azide-functionalized drugs which, after coupling to the vitamin, are released with a 4-(4-ethynylphenyl)-triazole functionality. Three chloroquine and one imidazolopiperazine derivative (based on the KAF156 structure) were selected as model drugs. One hybrid chloroquine conjugate was extensively studied via fluorescent labelling for in vitro and in vivo bio-distribution studies and gave proof-of-concept for the design. It showed no toxicity in vivo (zebrafish model) as well as no hepatotoxicity, no cardiotoxicity or developmental toxicity of the embryos. All 4-(4-ethynylphenyl)-triazole derivatives of chloroquine were equally active against chloroquine-resistant (CQR) and chloroquine-sensitive (CQS) Plasmodium falciparum strains.

Modified biovectors for the tuneable activation of anti-platelet carbon monoxide release

This communication describes the anti-platelet effects of a new class of cis-rhenium(ii)-dicarbonyl-vitamin B₁₂ complexes (B₁₂-ReCORMs) with tuneable CO releasing properties.

Organometallic cobalamin anticancer derivatives for targeted prodrug delivery via transcobalamin-mediated uptake

We report the synthesis and study of new water-soluble vitamin B₁₂ prodrugs bearing metal complexes at the β-upper side of the cobalt center for targeted prodrug delivery.

The evolution of personality in patients with mild cognitive impairment

AIMS

To describe personality traits and their changes in mild cognitive impairment (MCI) and control subjects.

METHODS

Sixty-three MCI and 90 control subjects were asked to describe their current personality traits by the Structured Interview for the Five-Factor Model (SIFFM). For each subject, a close relative retrospectively assessed these descriptions both as to the previous and current personality traits, using the Revised NEO Personality Inventory, Form R (NEO-PI-R).

RESULTS

Self-assessed MCI subjects reported significantly lower scores in the openness dimension than control subjects [F(1, 150) = 9.84, p = 0.002, ηp(2) = 0.06]. In current observer ratings, MCI subjects had higher scores on neuroticism [F(1, 137) = 7.55, p = 0.007, ηp(2) = 0.05] and lower ones on extraversion [F(1, 137) = 6.40, p = 0.013, ηp(2) = 0.04], openness [F(1, 137) = 9.93, p = 0.002, ηp(2) = 0.07], agreeableness [F(1, 137) = 10.18, p = 0.002, ηp(2) = 0.07] and conscientiousness [F(1, 137) = 25.96, p < 0.001, ηp(2) = 0.16]. Previous personality traits discriminated the groups as previous openness [odds ratio (OR) = 0.97, 95% confidence interval (CI) = 0.95-0.99, p = 0.014] and conscientiousness (OR = 0.96, 95% CI 0.94-0.98, p = 0.001) were negatively related to MCI group membership. In MCI subjects, conscientiousness [F(1, 137) = 19.20, p < 0.001, ηp(2) = 0.12] and extraversion [F(1, 137) = 22.27, p < 0.001, ηp(2) = 0.14] decreased between previous and current evaluations and neuroticism increased [F(1, 137) = 22.23, p < 0.001, ηp(2) = 0.14], whereas no significant change was found in control subjects.

CONCLUSIONS

MCI subjects undergo significant personality changes. Thus, personality assessment may aid the early detection of dementia.

Personality traits and behavioural and psychological symptoms in patients with mild cognitive impairment

BACKGROUND AND AIMS

Both personality changes and behavioural and psychological symptoms (BPS) may be associated with mild cognitive impairment (MCI) in later life and help identify incipient dementia. We wished to investigate the links between personality and BPS in MCI.

METHOD

We studied premorbid personality traits as estimated 5 years back and their changes in 83 control subjects and 52 MCI patients using the revised NEO Personality Inventory for the Five-Factor Model completed by a proxy. Information on BPS was obtained using the Neuropsychiatric Inventory (NPI). Analyses were controlled for current depression and anxiety.

RESULTS

Premorbid neuroticism and openness to experience were associated with the total NPI score. The changes in neuroticism, extraversion, openness to experiences, and conscientiousness were associated with apathy and affective symptoms.

CONCLUSIONS

Personality changes and BPS occur in MCI. The occurrence of affective BPS and apathy is associated with both premorbid personality traits and their changes.

[Personality and dementia: a new perspective]

This article highlights some of the links between pre-morbid personality and clinical features of dementia. Indeed, personality characteristics forge an individual's coping strategies and thus influence the expression of behavioural and psychiatric syndromes of dementia (BPSD) or its precursor stages. Some personality traits such as neuroticism may impact on cognitive decline. BPSD being among the most important determinants of a patient's and their proxies' burden, a better understanding of the links between pre-morbid personality characteristics and BPSD will help define care strategies.

Selection of oligonucleotides for whole-genome microarrays with semi-automatic update

Oligonucleotide microarray probes are designed to match specific transcripts present in databases that are regularly updated. As a consequence probes should be checked every new database release. We thus developed an informatics tool allowing the semi-automatic update of probe collections of long oligonucleotides and applied it to the mouse RefSeq database.

AVAILABILITY

http://www.bio.espci.fr/sol/

High-speed wave-mixing laser Doppler imaging in vivo

An interferometric method for parallel optical spectroscopy in the kilohertz range is reported, as well as its experimental validation in the context of high-speed laser Doppler imaging in vivo. The interferometric approach enables imaging in the low light conditions of a 2 kHz frame rate recording with a complementary metal-oxide semiconductor camera. Observation of mice craniums with near-infrared (lambda=785 nm) laser light in reflection configuration is reported. Doppler spectral images allegedly sensitive to blood flow are sequentially measured at several optical frequency detunings, to shift the spectral range of analysis in the radio-frequency spectrum.

Transmembrane protein 50b (C21orf4), a candidate for Down syndrome neurophenotypes, encodes an intracellular membrane protein expressed in the rodent brain

Transmembrane protein 50b, Tmem50b, previously referred to as C21orf4, encodes a predicted transmembrane protein and is one of few genes significantly over-expressed during cerebellar development in a Down syndrome mouse model, Ts1Cje. In order to assess potential mechanisms by which Tmem50b could contribute to Down syndrome-related phenotypes, we determined the expression patterns of Tmem50b mRNA, as well as Tmem50b protein distribution, expression and subcellular localization. In situ hybridization in mice at embryonic day 14.5 showed cortical plate and spinal cord mRNA expression. By postnatal day 7, strong mRNA expression was seen in the cerebellum, hippocampus and olfactory bulb, with diffuse cortical expression. Quantitative PCR of adult mouse tissue showed Tmem50b mRNA expression in the brain, heart and testis. A rabbit polyclonal antibody was generated against Tmem50b and rat and mouse tissue screening by Western blot, and immunohistochemistry showed that protein expression concurred with mRNA expression. Double immunofluorescence revealed that Tmem50b is highly expressed in rat and mouse glial fibrillary acidic protein-positive cells in vivo and in vitro, but less so in neuronal MAP2- or beta-tubulin II-positive cells in vitro. Tmem50b is invariably expressed in cultured mouse neural precursor cells. In adult mouse cerebellum sections, Tmem50b immunoreactivity was found in Purkinje and Golgi cell somata and in Bergmann glial processes. Electron microscopy confirmed that Tmem50b was present on endoplasmic reticulum (ER) and Golgi apparatus membranes. Results indicate that Tmem50b is a developmentally-regulated intracellular ER and Golgi apparatus membrane protein that may prove important for correct brain development through functions associated with precursor cells and glia.

Integrating whole transcriptome assays on a lab-on-a-chip for single cell gene profiling

To correlate gene expression profiles to fundamental biological processes such as cell growth, differentiation and migration, it is essential to work at the single cell level. Gene expression analysis always starts with the relatively low efficient reverse transcription (RT) of RNA into complementary DNA (cDNA), an essential step as unprocessed RNAs will not be analysed further. In this paper, we present a novel method for RT that uses microfluidics to manipulate nanolitre volumes. We compare our method to conventional protocols performed in microlitre volumes. More specifically, reverse transcription was performed either in a polydimethylsiloxane (PDMS) rotary mixer or in a tube, using a single cell amount of mouse brain RNA (10 pg), and was followed by a template-switching PCR (TS-PCR) amplification step. We demonstrate that, using the microfluidic protocol, 74% of the genes expressed in mouse brain were detected, while only 4% were found with the conventional approach. We next profiled single neuronal progenitors. Using our microfluidic approach, i.e. performing cell capture, lysis and reverse transcription on-chip followed by TS-PCR amplification in tube, a mean of 5000 genes were detected in each neuron, which corresponds to the expected number of genes expressed in a single cell. This demonstrates the outstanding sensitivity of the microfluidic method.

Classification of human chromosome 21 gene-expression variations in Down syndrome: impact on disease phenotypes

Down syndrome caused by chromosome 21 trisomy is the most common genetic cause of mental retardation in humans. Disruption of the phenotype is thought to be the result of gene-dosage imbalance. Variations in chromosome 21 gene expression in Down syndrome were analyzed in lymphoblastoid cells derived from patients and control individuals. Of the 359 genes and predictions displayed on a specifically designed high-content chromosome 21 microarray, one-third were expressed in lymphoblastoid cells. We performed a mixed-model analysis of variance to find genes that are differentially expressed in Down syndrome independent of sex and interindividual variations. In addition, we identified genes with variations between Down syndrome and control samples that were significantly different from the gene-dosage effect (1.5). Microarray data were validated by quantitative polymerase chain reaction. We found that 29% of the expressed chromosome 21 transcripts are overexpressed in Down syndrome and correspond to either genes or open reading frames. Among these, 22% are increased proportional to the gene-dosage effect, and 7% are amplified. The other 71% of expressed sequences are either compensated (56%, with a large proportion of predicted genes and antisense transcripts) or highly variable among individuals (15%). Thus, most of the chromosome 21 transcripts are compensated for the gene-dosage effect. Overexpressed genes are likely to be involved in the Down syndrome phenotype, in contrast to the compensated genes. Highly variable genes could account for phenotypic variations observed in patients. Finally, we show that alternative transcripts belonging to the same gene are similarly regulated in Down syndrome but sense and antisense transcripts are not.

Transcriptional disruptions in Down syndrome: a case study in the Ts1Cje mouse cerebellum during post-natal development

To understand the aetiology and the phenotypic severity of Down syndrome, we searched for transcriptional signatures in a substructure of the brain (cerebellum) during post-natal development in a segmental trisomy 16 model, the Ts1Cje mouse. The goal of this study was to investigate the effects of trisomy on changes in gene expression across development time. The primary gene-dosage effect on triplicated genes (approximately 1.5) was observed at birth [post-natal day 0 (P0)], at P15 and P30. About 5% of the non-triplicated genes were significantly differentially expressed between trisomic and control cerebellum, while 25% of the transcriptome was modified during post-natal development of the cerebellum. Indeed, only 165, 171 and 115 genes were dysregulated in trisomic cerebellum at P0, P15 and P30, respectively. Surprisingly, there were only three genes dysregulated in development and in trisomic animals in a similar or opposite direction. These three genes (Dscr1, Son and Hmg14) were, quite unexpectedly, triplicated in the Ts1Cje model and should be candidate genes for understanding the aetiology of the phenotype observed in the cerebellum.

The endogenous somnogen adenosine excites a subset of sleep-promoting neurons via A2A receptors in the ventrolateral preoptic nucleus

Recent research has shown that neurons in the ventrolateral preoptic nucleus are crucial for sleep by inhibiting wake-promoting systems, but the process that triggers their activation at sleep onset remains to be established. Since evidence indicates that sleep induced by adenosine, an endogenous sleep-promoting substance, requires activation of brain A(2A) receptors, we examined the hypothesis that adenosine could activate ventrolateral preoptic nucleus sleep neurons via A(2A) adenosine receptors in rat brain slices. Following on from our initial in vitro identification of these neurons as uniformly inhibited by noradrenaline and acetylcholine arousal transmitters, we established that the ventrolateral preoptic nucleus comprises two intermingled subtypes of sleep neurons, differing in their firing responses to serotonin, inducing either an inhibition (Type-1 cells) or an excitation (Type-2 cells). Since both cell types contained galanin and expressed glutamic acid decarboxylase-65/67 mRNAs, they potentially correspond to the sleep promoting neurons inhibiting arousal systems. Our pharmacological investigations using A(1) and A(2A) adenosine receptors agonists and antagonists further revealed that only Type-2 neurons were excited by adenosine via a postsynaptic activation of A(2A) adenosine receptors. Hence, the present study is the first demonstration of a direct activation of the sleep neurons by adenosine. Our results further support the cellular and functional heterogeneity of the sleep neurons, which could enable their differential contribution to the regulation of sleep. Adenosine and serotonin progressively accumulate during arousal. We propose that Type-2 neurons, which respond to these homeostatic signals by increasing their firing are involved in sleep induction. In contrast, Type-1 neurons would likely play a role in the consolidation of sleep.

National character does not reflect mean personality trait levels in 49 cultures

Most people hold beliefs about personality characteristics typical of members of their own and others' cultures. These perceptions of national character may be generalizations from personal experience, stereotypes with a "kernel of truth," or inaccurate stereotypes. We obtained national character ratings of 3989 people from 49 cultures and compared them with the average personality scores of culture members assessed by observer ratings and self-reports. National character ratings were reliable but did not converge with assessed traits. Perceptions of national character thus appear to be unfounded stereotypes that may serve the function of maintaining a national identity.

The cerebellar transcriptome during postnatal development of the Ts1Cje mouse, a segmental trisomy model for Down syndrome

The central nervous system of persons with Down syndrome presents cytoarchitectural abnormalities that likely result from gene-dosage effects affecting the expression of key developmental genes. To test this hypothesis, we have investigated the transcriptome of the cerebellum of the Ts1Cje mouse model of Down syndrome during postnatal development using microarrays and quantitative PCR (qPCR). Genes present in three copies were consistently overexpressed, with a mean ratio relative to euploid of 1.52 as determined by qPCR. Out of 63 three-copy genes tested, only five, nine and seven genes had ratios >2 or <1.2 at postnatal days 0 (P0), P15 and P30, respectively. This gene-dosage effect was associated with a dysregulation of the expression of some two-copy genes. Out of 8258 genes examined, the Ts1Cje/euploid ratios differed significantly from 1.0 for 406 (80 and 154 with ratios above 1.5 and below 0.7, respectively), 333 (11 above 1.5 and 55 below 0.7) and 246 genes (59 above 1.5 and 69 below 0.7) at P0, P15 and P30, respectively. Among the two-copy genes differentially expressed in the trisomic cerebellum, six homeobox genes, two belonging to the Notch pathway, were severely repressed. Overall, at P0, transcripts involved in cell differentiation and development were over-represented among the dysregulated genes, suggesting that cell differentiation and migration might be more altered than cell proliferation. Finally, global gene profiling revealed that transcription in Ts1Cje mice is more affected by the developmental changes than by the trisomic state, and that there is no apparent detectable delay in the postnatal development of the cerebellum of Ts1Cje mice.

Injection and flow control system for microchannels

In spite of considerable efforts, flow control in micro-channels remains a challenge owing to the very small ratio of channel/supply-system volumes, as well as the induction of spurious flows by extremely small pressure or geometry changes. We present here an inexpensive and robust system for flow control in a microchannel system, based on a dynamic control of reservoir pressures at the end of each channel. This system allows flow equilibration with a time constant smaller than one second, and is also able to maintain stable flux from stopped flow to many microl min(-1) range over several hours. It is robust to changes in ambient pressure and temperature. This system further includes a feature for sub-microliter sample injection during the experiment. We quantify flow control in elastomer and thermoplastic channels, and demonstrate the impact on one application of the system, namely the reproducible, automated separation of large DNA by electrophoresis in a self-organized magnetic bead matrix in a microchannel.

VARAN: a web server for variability analysis of DNA microarray experiments

Here, we describe a tool for VARiability Analysis of DNA microarrays experiments (VARAN), a freely available Web server that performs a signal intensity based analysis of the log2 expression ratio variability deduced from DNA microarray data (one or two channels). Two modules are proposed: VARAN generator to compute a sliding windows analysis of the experimental variability (mean and SD) and VARAN analyzer to compare experimental data with an asymptotic variability model previously built with the generator module from control experiments. Both modules provide normalized intensity signals with five possible methods, log ratio values and a list of genes showing significant variations between conditions.

AVAILABILITY

http://www.bionet.espci.fr/varan/

SUPPLEMENTARY INFORMATION

http://www.bionet.espci.fr/varan/help.html

Polyglutamylated .alpha.-tubulin can enter the tyrosination/detyrosination cycle

We have previously identified a major modification of neuronal alpha-tubulin which consists of the posttranslational addition of a varying number of glutamyl units on the gamma-carboxyl group of glutamate residue 445. This modification, called polyglutamylation, was initially found associated with detyrosinated alpha-tubulin [Eddé, B., Rossier, J., Le Caer, J.P., Desbruyères, E., Gros, F., & Denoulet, P. (1990) Science 247, 83-85]. In this report we show that a lateral chain of glutamyl units can also be present on tyrosinated alpha-tubulin. Incubation of cultured mouse brain neurons with radioactive tyrosine, in the presence of cycloheximide, resulted in a posttranslational labeling of six alpha-tubulin isoelectric variants. Because both tyrosination and polyglutamylation occur in the C-terminal region of alpha-tubulin, the structure of this region was investigated. [3H]tyrosinated tubulin was mixed with a large excess of unlabeled mouse brain tubulin and digested with thermolysin. Five peptides, detected by their radioactivity, were purified by high-performance liquid chromatography. Amino acid sequencing and mass spectrometry showed that one of these peptides corresponds to the native C-terminal part of alpha-tubulin 440VEGEGEEEGEEY451 and that the remainders bear a varying number of glutamyl units linked to glutamate residue 445, which explains the observed heterogeneity of tyrosinated alpha-tubulin. A quantitative analysis showed that the different tyrosinated forms of alpha-tubulin represent a minor (13%) fraction of the total alpha-tubulin present in the brain and that most (80%) of these tyrosinated forms are polyglutamylated.(ABSTRACT TRUNCATED AT 250 WORDS)

Structure of tubulin C-terminal domain obtained by subtilisin treatment The major α and β tubulin isotypes from pig brain are glutamylated

Limited subtilisin digestion of the tubulin alpha, beta heterodimer has been used in this work to reduce the total number of tubulin isotypes from 20 for native to 9 for subtilisin-cleaved tubulin. This indicates that the major part of tubulin heterogeneity is located at the C-terminus of the molecule. The C-terminal peptides of both alpha and beta subunits of tubulin were purified by anion-exchange HPLC. Combined use of Edman degradation chemistry and mass spectrometry on the isolated peptides shows that subtilisin cleavage occurs at position Asp-438 and His-406 of alpha and Gln-433 and His-396 of beta tubulin chains. Quantitative analysis of our data show that cleavage at positions His-406 (alpha) and His-396 (beta) occurs with a low efficiency and indicates that the major isotypes of pig brain tubulin are modified by sequential attachment of 1 to 5 glutamic acid residues at positions Glu-445 or -435 of alpha and beta tubulin, respectively.

Characterization of new enkephalin-containing peptides in the adrenal medulla by immunoblotting

Immunoblotting combined with radioimmunoassays (RIAs) directed specifically towards certain sequences of the proenkephalin molecule has been used to characterize the enkephalin-containing peptides (ECPs) present in the bovine adrenal medulla. Immunoblotting allowed the simultaneous visualization of all ECPs present in a crude extract of this gland. Combining this technique with RIAs we have been able to characterize a new high molecular mass ECP, a 23.3-kDa protein which contains the amino-terminal part of proenkephalin and ends with the sequence of Leu-enkephalin at its carboxy-terminus.

Peptidic determinants and structural model of human NDP kinase B (Nm23-H2) bound to single-stranded DNA

Isoform B of human NDP kinase (NDPK-B) was previously identified as a transcription factor stimulating in vitro and ex vivo the transcription of the c-myc oncogene, which involves this enzyme in carcinogenesis. We have studied the enzymatic properties of NDPK-B in the presence of several single-stranded oligonucleotides. We show that the oligonucleotides are competitive inhibitors of the catalytic activity, indicating that the active site acts as a binding template for the anchorage of the oligonucleotide. Furthermore, the presence of a guanine at the 3'-end of several different aptamers increases its affinity 10-fold. To define the surface of the protein contacting the DNA within the nucleoprotein complex, we used single nanosecond laser pulses as the cross-linking reagent and MALDI-TOF mass spectrometry to identify cross-linked peptides purified from proteolytic digests of the cross-linked complex. Using 11-mer and 30-mer single-stranded oligonucleotides, the same three different nucleopeptides were identified after irradiation of the complexes, indicating a common binding mode for these two aptamers. Taken together, these results allowed us to propose a structural model of NDPK-B bound to single-stranded DNA.

Selection and identification of proteins bound to DNA triple-helical structures by combination of 2D-electrophoresis and MALDI-TOF mass spectrometry

Identification of proteins binding specifically to peculiar nucleic acid structures can lead to comprehension of their role in vivo and contribute to the discovery of structure-related gene regulation. This work was devoted to establishing a reliable procedure to select proteins on the basis of their interaction with a nucleic acid probe chosen to fold into a given structure. 2D-electrophoresis and mass spectrometry were combined for protein identification. We applied this procedure to select and identify triplex-binding activities in HeLa nuclear extracts. To achieve this, we used a panel of deoxyribonucleic probes adopting intramolecular triple-helices, varying in their primary sequence, structure or triple-helix motif. A limited number of spots was reproducibly revealed by South-western blotting. Spots of interest were localised among a complex population of (35)S-labelled proteins according to their (32)P-specific emission. Position of the same spots was extrapolated on a preparative gel coloured with Coomassie blue, allowing excision and purification of the corresponding proteins. The material was subjected to mass spectrometry upon trypsin digestion and MALDI-TOF peptide fingerprinting was used for research in databases: five of them were identified and found to belong to the hnRNP family (K, L, A2/B1, E1 and I). The identities of several of them were confirmed by comparing western and South-western blots on the same membrane using specific antibodies. The recognition specificity of most of these proteins is large, according to previous reports and our own experiments. It includes pyrimidine-rich DNA sequences in different contexts: single strand to a small extent, triplex and possibly other higher-order structures.

Absolute quantification of AMPA receptor subunit mRNAs in single hippocampal neurons

alpha-Amino-3-hydroxy-5-methylisoxazole-4-propionate (AMPA) receptor subunit (GluR1-4) mRNAs expressed by single neurons in rat hippocampal cultures were quantified by single-cell RT-PCR using an internal standard RNA after whole-cell patch-clamp recording. The internal standard RNA, derived from GluR2 with a single nucleotide substitution, was reverse-transcribed and PCR-amplified with the same efficiency as GluR1-4 mRNAs. The mean mRNA numbers harvested in vitro from pyramidal-like neurons on day 9 were 1150 +/- 324 molecules of GluR1, 1080 +/- 273 molecules of GluR2, 100 +/- 20 molecules of GluR3, and 50 +/- 10 molecules of GluR4 (mean +/- SEM, n = 12). In a non-pyramidal neuronal population that expresses AMPA receptors characterized by high Ca(2+) permeability, the numbers of GluR1, GluR3 and GluR4 mRNA molecules harvested per cell were 354 +/- 64, 25 +/- 17 and 168 +/- 36, respectively (n = 8). The GluR2 mRNA was not detected in this cell type. The calculated ratio of AMPAR mRNA molecules per total mRNA molecules was 1/240 in pyramidal-like neurons (1/500 for GluR2), being in the range obtained with total RNA from rat forebrain and cerebellum (1/170 and 1/380, respectively). Finally, our results indicated that the proportion of GluR1-4 mRNA located in neurites reached approximately 60% in pyramidal-like neurons. However, we found no evidence of preferential subcellular distribution of a given subunit.

Ponericins, new antibacterial and insecticidal peptides from the venom of the ant Pachycondyla goeldii

The antimicrobial, insecticidal, and hemolytic properties of peptides isolated from the venom of the predatory ant Pachycondyla goeldii, a member of the subfamily Ponerinae, were investigated. Fifteen novel peptides, named ponericins, exhibiting antibacterial and insecticidal properties were purified, and their amino acid sequences were characterized. According to their primary structure similarities, they can be classified into three families: ponericin G, W, and L. Ponericins share high sequence similarities with known peptides: ponericins G with cecropin-like peptides, ponericins W with gaegurins and melittin, and ponericins L with dermaseptins. Ten peptides were synthesized for further analysis. Their antimicrobial activities against Gram-positive and Gram-negative bacteria strains were analyzed together with their insecticidal activities against cricket larvae and their hemolytic activities. Interestingly, within each of the three families, several peptides present differences in their biological activities. The comparison of the structural features of ponericins with those of well-studied peptides suggests that the ponericins may adopt an amphipathic alpha-helical structure in polar environments, such as cell membranes. In the venom, the estimated peptide concentrations appear to be compatible with an antibacterial activity in vivo. This suggests that in the ant colony, the peptides exhibit a defensive role against microbial pathogens arising from prey introduction and/or ingestion.

Kainate receptors regulate unitary IPSCs elicited in pyramidal cells by fast-spiking interneurons in the neocortex

Unitary IPSCs elicited by fast-spiking (FS) interneurons in layer V pyramidal cells of the neocortex were studied by means of dual whole-cell recordings in acute slices. FS to pyramidal cell unitary IPSCs were depressed by (RS)-S-amino-3-(3-hydroxy-5-tert-butylisoxazol-4-yl) (ATPA), a kainate (KA) receptor agonist, and by the endogenous agonist l-glutamate in the presence of AMPA, NMDA, mGluR, and GABA(B) receptor antagonists. This effect was accompanied by an increase in failure rate of synaptic transmission, in the coefficient of variation, and in the paired pulse ratio, indicating a presynaptic origin of the IPSC depression. Pairing the activation of the presynaptic neuron with a depolarization of the postsynaptic cell mimicked the decrease of unitary IPSCs, and this effect persisted when postsynaptic sodium action potentials were blocked with the local anesthetic QX314. The effects of ATPA, glutamate, and of the pairing protocol were almost totally blocked by CNQX. These data suggest that KA receptors located on presynaptic FS cell terminals decrease the release of GABA and can be activated by glutamate released from the somatodendritic compartment of the postsynaptic pyramidal cells.

An optimized procedure for detection of proteins on carrier ampholyte isoelectric focusing and immobilized pH gradient gels with imidazole and zinc salts: its application to the identification of isoelectric focusing separated isoforms by in-gel proteolysis and mass spectrometry analysis

A method for the characterization of proteins separated by isoelectric focusing in carrier ampholytes (CA-IEF) or immobilized pH gradient (IPG) gels by in-gel digestion and mass spectrometry is described. Proteins are detected by an improved imidazole-Sodium dodecyl sulfate (SDS)-zinc staining adapted for IEF and IPG gels. Sensitivity is close to that of mass spectrometry-compatible silver staining, but simpler and faster. Proteins were digested in imidazole-SDS-zinc stained CA-IEF and IPG gels in the presence of a zinc-chelating agent. Mass spectra were clearly interpretable as carrier ampholytes which were efficiently removed before digestion; high-sequence coverage that allowed isoform characterization was obtained by analyzing both the aqueous and the organic phase extracts.

Auditory cues support place navigation in rats when associated with a visual cue

Rats, like other crepuscular animals, have excellent auditory capacities and they discriminate well between different sounds [Heffner HE, Heffner RS, Hearing in two cricetid rodents: wood rats (Neotoma floridana) and grasshopper mouse (Onychomys leucogaster). J Comp Psychol 1985;99(3):275-88]. However, most experimental literature concerning spatial orientation almost exclusively emphasizes the use of visual landmarks [Cressant A, Muller RU, Poucet B. Failure of centrally placed objects to control the firing fields of hippocampal place cells. J Neurosci 1997;17(7):2531-42; and Goodridge JP, Taube JS. Preferential use of the landmark navigational system by head direction cells in rats. Behav Neurosci 1995;109(1):49-61]. To address the important issue of whether rats are able to achieve a place navigation task relative to auditory beacons, we designed a place learning task in the water maze. We controlled cue availability by conducting the experiment in total darkness. Three auditory cues did not allow place navigation whereas three visual cues in the same positions did support place navigation. One auditory beacon directly associated with the goal location did not support taxon navigation (a beacon strategy allowing the animal to find the goal just by swimming toward the cue). Replacing the auditory beacons by one single visual beacon did support taxon navigation. A multimodal configuration of two auditory cues and one visual cue allowed correct place navigation. The deletion of the two auditory or of the one visual cue did disrupt the spatial performance. Thus rats can combine information from different sensory modalities to achieve a place navigation task. In particular, auditory cues support place navigation when associated with a visual one.

Protein analysis by mass spectrometry and sequence database searching: a proteomic approach to identify human lymphoblastoid cell line proteins

Lymphoblastoid cell lines correspond to in vitro EBV-immortalized lymphocyte B-cells. These cells display a suitable model for experiments dealing with changes in protein expression occurring upon B-cell differentiation, after drug treatment, or after inhibition of some transcription factors. For all these reasons we have undertaken an effort aimed at developing a hematopoietic cell line protein two-dimensional electrophoresis (2-DE) database, containing B-lymphoblastoid 2-DE maps. In this work, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) peptide mass fingerprinting analysis was adopted for protein identification. The peptide mass fingerprinting identification and the sequence coverage obtained on colloidal Coomassie blue (CBB) stained gel was close to that obtained using zinc-imidazole staining. Everything considered, CBB being more comfortable for subsequent spot manipulations, CBB staining was chosen for identification of a larger number of polypeptides. The results suggest that reticulation of the gel can interfere preventing the uptake of the enzyme during the in-gel digestion step. Consequently, low molecular mass proteins appear more difficult to identify by mass fingerprinting. Finally, the information provided in this study allows the construction of a new annoted reference map of human lymphoblastoid cell proteins. Among the identified proteins 60% were not yet positioned on 2-DE maps in three of the most important well-documented databases. The annoted map will be accessible via Internet on the LBPP server at URL:http:// www-smbh.univ-paris13.fr/lbtp/index.htm.

Classification of fusiform neocortical interneurons based on unsupervised clustering

A classification of fusiform neocortical interneurons (n = 60) was performed with an unsupervised cluster analysis based on the comparison of multiple electrophysiological and molecular parameters studied by patch-clamp and single-cell multiplex reverse transcription-PCR in rat neocortical acute slices. The multiplex reverse transcription-PCR protocol was designed to detect simultaneously the expression of GAD65, GAD67, calbindin, parvalbumin, calretinin, neuropeptide Y, vasoactive intestinal peptide (VIP), somatostatin (SS), cholecystokinin, alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid, kainate, N-methyl-d-aspartate, and metabotropic glutamate receptor subtypes. Three groups of fusiform interneurons with distinctive features were disclosed by the cluster analysis. The first type of fusiform neuron (n = 12), termed regular spiking nonpyramidal (RSNP)-SS cluster, was characterized by a firing pattern of RSNP cells and by a high occurrence of SS. The second type of fusiform neuron (n = 32), termed RSNP-VIP cluster, predominantly expressed VIP and also showed firing properties of RSNP neurons with accommodation profiles different from those of RSNP-SS cells. Finally, the last type of fusiform neuron (n = 16) contained a majority of irregular spiking-VIPergic neurons. In addition, the analysis of glutamate receptors revealed cell-type-specific expression profiles. This study shows that combinations of multiple independent criteria define distinct neocortical populations of interneurons potentially involved in specific functions.

Identification of sleep-promoting neurons in vitro

The neurons responsible for the onset of sleep are thought to be located in the preoptic area and more specifically, in the ventrolateral preoptic nucleus (VLPO). Here we identify sleep-promoting neurons in vitro and show that they represent an homogeneous population of cells that must be inhibited by systems of arousal during the waking state. We find that two-thirds of the VLPO neurons are multipolar triangular cells that show a low-threshold spike. This proportion matches that of cells active during sleep in the same region. We then show, using single-cell reverse transcriptase followed by polymerase chain reaction, that these neurons probably contain gamma-aminobutyric acid (GABA). We also show that these neurons are inhibited by noradrenaline and acetylcholine, both of which are transmitters of wakefulness. As most of these cells are also inhibited by serotonin but unaffected by histamine, their overall inhibition by transmitters of wakefulness is in agreement with their relative inactivity during waking with respect to sleep. We propose that the reciprocal inhibitory interaction of such VLPO neurons with the noradrenergic, serotoninergic and cholinergic waking systems to which they project is a key factor for promoting sleep.

The place preference task: a new tool for studying the relation between behavior and place cell activity in rats

This study describes a task that combines random searching with goal directed navigation. The testing was conducted on a circular elevated open field (80 cm in diameter), with an unmarked target area (20 cm in diameter) in the center of 1 of the 4 quadrants. Whenever the rat entered the target area, the computerized tracking system released a pellet to a random point on the open field. Rats were able to learn the task under light and in total darkness, and on a stable or a rotating arena. Visual information was important in light, but idiothetic information became crucial in darkness. Learning of a new position was quicker under light than in total darkness on a rotating arena. The place preference task should make it possible to study place cells (PCs) when the rats use an allothetic (room frame) or idiothetic (arena frame) representation of space and to compare the behavioral response with the PCs' activity.

Probing the native structure of stathmin and its interaction domains with tubulin. Combined use of limited proteolysis, size exclusion chromatography, and mass spectrometry

Stathmin is a cytosoluble phosphoprotein proposed to be a regulatory relay integrating diverse intracellular signaling pathway. Its interaction with tubulin modulates microtubule dynamics by destabilization of assembled microtubules or inhibition of their polymerization from free tubulin. The aim of this study was to probe the native structure of stathmin and to delineate its minimal region able to interact with tubulin. Limited proteolysis of stathmin revealed four structured domains within the native protein, corresponding to amino acid sequences 22-81 (I), 95-113 (II), 113-128 (III), and 128-149 (IV), which allows us to propose stathmin folding hypotheses. Furthermore, stathmin proteolytic fragments were mixed to interact with tubulin, and those that retained affinity for tubulin were isolated by size exclusion chromatography and identified by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. The results indicate that, to interact with tubulin, a stathmin fragment must span a minimal core region from residues 42 to 126, which interestingly corresponds to the predicted alpha-helical "interaction region" of stathmin. In addition, an interacting stathmin fragment must include a short N- or C-terminal extension. The functional significance of these interaction constrains is further validated by tubulin polymerization inhibition assays with fragments designed on the basis of the tubulin binding results. The present results will help to optimize further stathmin structural studies and to develop molecular tools to target its interaction with tubulin.

Postsynaptic glutamate receptors and integrative properties of fast-spiking interneurons in the rat neocortex

The glutamate-mediated synaptic responses of neocortical pyramidal cell to fast-spiking interneuron (pyramidal-FS) connections were studied by performing paired recordings at 30-33 degrees C in acute slices of 14- to 35-day-old rats (n = 39). Postsynaptic fast-spiking (FS) cells were recorded in whole cell configuration with a patch pipette, and presynaptic pyramidal cells were impaled with sharp intracellular electrodes. At a holding potential of -72 mV (near the resting membrane potential), unitary excitatory postsynaptic potentials (EPSPs) had a mean amplitude of 2.1 +/- 1.3 mV and a mean width at half-amplitude of 10.5 +/- 3.7 ms (n = 18). Bath application of the N-methyl-D-aspartate (NMDA) receptor antagonist D(-)2-amino-5-phosphonovaleric acid (D-AP5) had minor effects on both the amplitude and the duration of unitary EPSPs, whereas the alpha-amino-3-hydroxy-5-methyl-4-isoxazole-propionate (AMPA)/kainate receptor antagonist 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) almost completely blocked the synaptic responses. In voltage-clamp mode, the selective antagonist of AMPA receptors 1-(4-aminophenyl)-3-methylcarbamyl-4-methyl-7,8-methylenedioxy-3, 4-dihydro-5H-2,3-benzodiazepine (GYKI 53655; 40-66 microM) blocked 96 +/- 1.9% of D-AP5-insensitive unitary excitatory postsynaptic currents (EPSCs), confirming the predominance of AMPA receptors, as opposed to kainate receptors, at pyramidal-FS connections (n = 3). Unitary EPSCs mediated by AMPA receptors had fast rise times (0.29 +/- 0.04 ms) and amplitude-weighted decay time constants (2 +/- 0.8 ms; n = 16). In the presence of intracellular spermine, these currents showed the characteristic rectifying current-voltage (I-V) curve of calcium-permeable AMPA receptors. A slower component mediated by NMDA receptors was observed when unitary synaptic currents were recorded at a membrane potential more positive than -50 mV. In response to short trains of moderately high-frequency (67 Hz) presynaptic action potentials, we observed only a limited temporal summation of unitary EPSPs, probably because of the rapid kinetics of AMPA receptors and the absence of NMDA component in these subthreshold synaptic responses. By combining paired recordings with extracellular stimulations (n = 11), we demonstrated that EPSPs elicited by two different inputs were summed linearly by FS interneurons at membrane potentials below the action potential threshold. We estimated that, in our in vitro recording conditions, 8 +/- 5 pyramidal cells (n = 18) should be activated simultaneously to make FS interneurons fire an action potential from -72 mV. The low level of temporal summation and the linear summation of excitatory inputs in FS cells favor the role of coincidence detectors of these interneurons in neocortical circuits.

Selective excitation of subtypes of neocortical interneurons by nicotinic receptors

The cellular mechanisms by which neuronal nicotinic cholinergic receptors influence many aspects of physiology and pathology in the neocortex remain primarily unknown. Whole-cell recordings and single-cell reverse transcription (RT)-PCR were combined to analyze the effect of nicotinic receptor agonists on different types of neurons in acute slices of rat neocortex. Nicotinic receptor agonists had no effect on pyramidal neurons and on most types of interneurons, including parvalbumin-expressing fast spiking interneurons and somatostatin-expressing interneurons, but selectively excited a subpopulation of interneurons coexpressing the neuropeptides vasoactive intestinal peptide (VIP) and cholecystokinin. This excitation persisted in the presence of glutamate, GABA, and muscarinic receptor antagonists and in the presence of tetrodotoxin and low extracellular calcium, suggesting that the depolarization was mediated through the direct activation of postsynaptic nicotinic receptors. The responses were blocked by the nicotinic receptor antagonists dihydro-beta-erythroidine and mecamylamine and persisted in the presence of the alpha7 selective nicotinic receptor antagonist methyllycaconitine, suggesting that the involved nicotinic receptors lacked the alpha7 subunit. Single-cell RT-PCR analysis indicated that the majority of the interneurons that responded to nicotinic stimulation coexpressed the alpha4, alpha5, and beta2 nicotinic receptor subunits. Therefore, these results provide a role for non-alpha7 nicotinic receptors in the selective excitation of a subpopulation of neocortical interneurons. Because the neocortical interneurons expressing VIP have been proposed previously to regulate regional cortical blood flow and metabolism, these results also provide a cellular basis for the neuronal regulation of cortical blood flow mediated by acetylcholine.

Incremental conductance levels of GABAA receptors in dopaminergic neurones of the rat substantia nigra pars compacta

1. Molecular and biophysical properties of GABAA receptors of dopaminergic (DA) neurones of the pars compacta of the rat substantia nigra were studied in slices and after acute dissociation. 2. Single-cell reverse transcriptase-multiplex polymerase chain reaction confirmed that DA neurones contained mRNAs encoding for the alpha3 subunit of the GABAA receptor, but further showed the presence of alpha4 subunit mRNAs. alpha2, beta1 and gamma1 subunit mRNAs were never detected. Overall, DA neurones present a pattern of expression of GABAA receptor subunit mRNAs containing mainly alpha3/4beta2/3gamma3. 3. Outside-out patches were excised from DA neurones and GABAA single-channel patch-clamp currents were recorded under low doses (1-5 microM) of GABA or isoguvacine, a selective GABAA agonist. Recordings presented several conductance levels which appeared to be integer multiples of an elementary conductance of 4-5 pS. This property was shared by GABAA receptors of cerebellar Purkinje neurones recorded in slices (however, with an elementary conductance of 3 pS). Only the 5-6 lowest levels were analysed. 4. A progressive change in the distribution of occupancy of these levels was observed when increasing the isoguvacine concentration (up to 10 microM) as well as when adding zolpidem (20-200 nM), a drug acting at the benzodiazepine binding site: both treatments enlarged the occupancy of the highest conductance levels, while decreasing that of the smallest ones. Conversely, Zn2+ (10 microM), a negative allosteric modulator of GABAA receptor channels, decreased the occupancy of the highest levels in favour of the lowest ones. 5. These properties of alpha3/4beta2/3gamma3-containing GABAA receptors would support the hypothesis of either single GABAA receptor channels with multiple open states or that of a synchronous recruitment of GABAA receptor channels that could involve their clustering in the membranes of DA neurones.

Structural characterization by tandem mass spectrometry of the posttranslational polyglycylation of tubulin

Polyglycylation is a posttranslational modification specific to tubulin. This modification was originally identified in highly stable microtubules from Paramecium cilia. As many as 34 posttranslationally added glycine residues have been located in the C-terminal domains of Paramecium alpha- and beta-tubulin. In this study, post source decay matrix-assisted laser desorption/ionization mass spectrometry (PSD MALDI MS) and electrospray ionization on a hybrid quadrupole orthogonal time-of-flight tandem mass spectrometer (ESI Q-TOF MS/MS) were both used to demonstrate that a single molecule of beta-tubulin, from either dynamic cytoplasmic microtubules or stable axonemal microtubules, can be glycylated on each of the last four C-terminal glutamate residues Glu437, Glu438, Glu439, and Glu441 in the sequence 427DATAEEEGEFEEEGEQ442. In both dynamic and stable microtubules the most abundant beta-tubulin isoform contains six posttranslationally added glycine residues: two glycine residues on both Glu437 and Glu438 and one glycine residue on both Glu439 and Glu441. The number and relative abundance of glycylated isoforms of beta-tubulin in both cytoplasmic and axonemal microtubules were compared by MALDI MS.1 The abundance of the major glycylated isoforms in axonemal tubulin decreases regularly with glycylation levels from 6 to 19 whereas it drops abruptly in cytoplasmic tubulin with glycylation levels from 6 to 9. However, the polyglycine chains are similarly distributed on the four C-terminal glutamate residues of cytoplasmic and axonemal tubulin. The polyglycylation results in bulky C-terminal domains with negatively charged surfaces, all surrounding the microtubular structure.

Developmental synaptic changes increase the range of integrative capabilities of an identified excitatory neocortical connection

Excitatory synaptic transmission between pyramidal cells and fast-spiking (FS) interneurons of layer V of the motor cortex was investigated in acute slices by using paired recordings at 30 degrees C combined with morphological analysis. The presynaptic and postsynaptic properties at these identified central synapses were compared between 3- and 5-week-old rats. At these two postnatal developmental stages, unitary EPSCs were mediated by the activation of AMPA receptors with fast kinetics at a holding potential of -72 mV. The amplitude distribution analysis of the EPSCs indicates that, at both stages, pyramidal-FS connections consisted of multiple functional release sites. The apparent quantal size obtained by decreasing the external calcium ([Ca2+]e) varied from 11 to 29 pA near resting membrane potential. In young rats, pairs of presynaptic action potentials elicited unitary synaptic responses that displayed paired-pulse depression at all tested frequencies. In older animals, inputs from different pyramidal cells onto the same FS interneuron had different paired-pulse response characteristics and, at most of these connections, a switch from depression to facilitation occurred when decreasing the rate of presynaptic stimulation. The balance between facilitation and depression endows pyramidal-FS connections from 5-week-old animals with wide integrative capabilities and confers unique functional properties to each synapse.

Basal body duplication in Paramecium requires gamma-tubulin

First discovered in the fungus Aspergillus nidulans[1], gamma-tubulin is a ubiquitous component of microtubule organizing centres [2]. In centrosomes, gamma-tubulin has been immunolocalized at the pericentriolar material, suggesting a role in cytoplasmic microtubule nucleation [3], as well as within the centriole core itself [4]. Although its function in the nucleation of the mitotic spindle and of cytoplasmic interphasic microtubules has been demonstrated in vitro [5] [6] and in vivo[7] [8] [9], the hypothesis that gamma-tubulin could intervene in centriole assembly has never been experimentally addressed because the mitotic arrest caused by the inactivation of gamma-tubulin in vivo precludes any further phenotypic analysis of putative centriole defects. The issue can be addressed in the ciliate Paramecium, which is characterized by numerous basal bodies that are similar to centrioles but the biogenesis of which is not tightly coupled to the nuclear division cycle. We demonstrate that the inactivation of the Paramecium gamma-tubulin genes leads to inhibition of basal body duplication.

Properties of bipolar VIPergic interneurons and their excitation by pyramidal neurons in the rat neocortex

In the rat neocortex, a subset of GABAergic interneurons express the neuropeptide vasoactive intestinal peptide (VIP). Previously, we demonstrated that a population of VIPergic interneurons could be accurately identified by their irregular spiking (IS) pattern and their bipolar morphology. IS interneurons were studied in neocortical slices from 16-22-day-old rats using whole-cell recordings, intracellular labelling and single-cell RT-PCR. In response to a depolarizing pulse, IS interneurons typically discharged a burst of action potentials followed by spikes emitted at an irregular frequency. Several seconds of depolarization, micromolar concentrations of 4-aminopyridine, and nanomolar concentrations of either dendrotoxin I or K converted this irregular pattern to a sustained discharge, suggesting the involvement of an ID-like K+ current. The main glutamate receptor subunits detected in IS cells were GluR1 flop and GluR2 flop, GluR5 and GluR6, and NR2B and NR2D for the alpha-amino-3-hydroxyl-5-methyl-4-isoxazolepropionic acid (AMPA), kainate and N-methyl-D-aspartic acid (NMDA) subtypes, respectively. Paired whole-cell patch-clamp recordings indicated that pyramidal neurons provide intracortical glutamatergic inputs onto IS interneurons. Most connections had high probabilities of response and exhibited frequency-dependent paired pulse depression. Comparison of the amplitude distribution of paired responses suggested that most of these connections consisted of multiple functional release sites. Finally, two discrete subpopulations of IS cells could be identified based on the duration of the initial burst of action potentials and the differential expression of calretinin and choline acetyltransferase.