Lymphoid environment limits superantigen and antigen-induced T cell proliferation at high precursor frequency.

After superantigen challenge a significant proportion of superantigen-reactive T cells remain undivided. We provide evidence that the lymphoid environment limits T cell proliferation in the secondary lymphoid organs when the frequency of superantigen reactive T cells is unusually high. We monitored T cell proliferation and the percentage of undivided cells when the frequency of superantigen-reactive T cells was low (1%), intermediate (15%) or high (30-100%) by transferring fluorescently labeled cells into different recipients. When the frequency was low, practically all the reactive T cells entered cell cycle and proliferated maximally. At intermediate frequencies a large proportion of reactive T cells did not enter cell cycle and the whole population divided less. A further increase in reactive T cells did not alter the percentage of undivided cells but induced a further decrease in the number of cell divisions. Interestingly, the observations made with superantigens were confirmed with peptide antigen and TCR-transgenic mice. Moreover, in vivo and in vitro data suggest that dendritic cells are the most likely candidates in limiting T cell proliferation in the lymphoid environment. In conclusion, we show that the availability of APC in the lymphoid environment can quantitatively limit T cell priming.

High prevalence and low E6 genetic variability of human papillomavirus 58 in women with cervical cancer and precursor lesions in Southeast Mexico

Infection with some genotypes of human papillomavirus (HPV) is the most important risk factor associated with cervical cancer (CC). Throughout the world, HPV type 58 prevalence varies from one region to another; it is higher in women from certain countries in Asia and Latin America, such as China and Mexico. Although intratypic variants have been reported on a few occasions, our knowledge about HPV 58 genetic variation remains limited. Therefore, this work aims to (i) determine the prevalence of HPV type 58 amongst Mexican women with invasive CC or precursor lesions and (ii) identify HPV 58 sequence variants. One hundred and forty five colposcopy clinic patients were studied. Genotyping of HPV 16, 18 and 58 was determined by specific nested PCR and HPV 58 variants were detected by direct sequencing. The general prevalence of HPV was 51.7% (75/145). HPV 16 was found in 30.6% (23/75) and HPV 58 in 24% (18/75) of the patients. HPV 18 was not identified in patients with cervical intraepithelial neoplasia (CIN) grade I; it was only found in those with CIN II, with a prevalence of 6.8% (3/44). In patients with CC, the prevalence of HPV 16 and 58 was 78.9%. Regarding HPV 58 variants, 94.4% of the HPV 58 sequences were identical to the prototype strain, whereas one sample showed changes at a single nucleotide. This study demonstrates a high prevalence of HPV 58 and a low genetic variability of E6 sequences amongst Mexican colposcopy patients.

Precursor ion scans for the targeted detection of stable-isotope-labeled peptides.

Stable isotope labels are routinely introduced into proteomes for quantification purposes. Full labeling of cells in varying biological states, followed by sample mixing, fractionation and intensive data acquisition, is used to obtain accurate large-scale quantification of total protein levels. However, biological processes often affect only a small group of proteins for a short time, resulting in changes that are difficult to detect against the total proteome background. An alternative approach could be the targeted analysis of the proteins synthesized in response to a given biological stimulus. Such proteins can be pulse-labeled with a stable isotope by metabolic incorporation of 'heavy' amino acids. In this study we investigated the specific detection and identification of labeled proteins using acquisition methods based on Precursor Ion Scans (PIS) on a triple-quadrupole ion trap mass spectrometer. PIS-based methods were set to detect unique immonium ions originating from labeled peptides. Different labels and methods were tested in standard mixtures to optimize performance. We showed that, in comparison with an untargeted analysis on the same instrument, the approach allowed a several-fold increase in the specificity of detection of labeled proteins over unlabeled ones. The technique was applied to the identification of proteins secreted by human cells into growth media containing bovine serum proteins, allowing the preferential detection of labeled cellular proteins over unlabeled bovine ones. However, compared with untargeted acquisitions on two different instruments, the PIS-based strategy showed some limitations in sensitivity. We discuss possible perspectives of the technique.

Síntesi de la molècula ML-10 i del seu precursor immediat per poder obtenir 18F-ML-10, d'ús en tècniques PET

El 18F-ML-10 és un radiofàrmac utilitzat com a traçador de cèl·lules apoptòtiques mitjançant la tècnica del PET (Positron Emission Tomography). En el present treball de recerca s’ha dut a terme la síntesi de dos precursors del 18F-ML-10, i del producte final no marcat isotòpicament, el ML-10. S’ha plantejat una síntesi convergent per l’obtenció del compost final 3, partint del malonat de di-tert-butil i l’1,5-pentandiol. Tant el precursor tosilat 1 com el mesilat 2 s’han sintetitzat en 3 etapes amb un 29% i un 36% de rendiment, respectivament. El compost 3, utilitzat com a referència en la síntesi del 18F-ML-10, s’ha sintetitzat en 2 etapes a partir del precursor 2 amb un rendiment total de la síntesi del 31%. El procés de radiomarcació s’està portant a terme a l’Institut d’Alta Tecnologia – Parc de Recerca Biomèdica de Barcelona (IAT–PRBB), on posteriorment es faran estudis neurològics i oncològics on el seguiment de processos apoptòtics és clau.

Glutathione Precursor, N-Acetyl-Cysteine, Modulates EEG Synchronization in Schizophrenia Patients

Background: Glutathione (GSH) dysregulation at the gene, protein and functional levels observed in schizophrenia patients, and schizophrenia-like anomalies in GSH deficit experimental models, suggest that genetic glutathione synthesis impairments represent one major risk factor for the disease (Do et al., 2009). In a randomized, double blind, placebo controlled, add-on clinical trial of 140 patients, the GSH precursor N-Acetyl-Cysteine (NAC, 2g/day, 6 months) significantly improved the negative symptoms and reduced sideeffects due to antipsychotics (Berk et al., 2008). In a subset of patients (n=7), NAC (2g/day, 2 months, cross-over design) also improved auditory evoked potentials, the NMDA-dependent mismatch negativity (Lavoie et al, 2008). Methods: To determine whether increased GSH levels would modulate the topography of functional brain connectivity, we applied a multivariate phase synchronization (MPS) estimator (Knyazeva et al, 2008) to dense-array EEGs recorded during rest with eyes closed at the protocol onset, the point of crossover, and at its end. Results: The whole-head imaging revealed a specific synchronization landscape in NAC compared to placebo condition. In particular, NAC increased MPS over frontal and left temporal regions in a frequency-specific manner. The topography and direction of MPS changes were similar and robust in all 7 patients. Moreover, these changes correlated with the changes in the Liddle's score of disorganization, thus linking EEG synchronization to the improvement of the clinical picture. Conclusions: The data suggest an important pathway towards new therapeutic strategies that target GSH dysregulation in schizophrenia. They also show the utility of MPS mapping as a marker of treatment efficacy.

Coulier, Paul-Jean (1824-1890) : a precursor in the history of fingermark detection and their potential use for identifying their source (1863)

An online copy of a 1863 French book, The Scientific and Industrial Year (English translation of the title), that predates other historically significant writings about fingerprints suggests the use of iodine stains to reproduce papillary lines of the skin and suggests the feasibility of identifying suspects by touch. It also suggests the use of a magnifying glass for comparing those impressions whose origins need to be determined.

Glutathione precursor, N-acetyl-cysteine, improves mismatch negativity in schizophrenia patients.

In schizophrenia patients, glutathione dysregulation at the gene, protein and functional levels, leads to N-methyl-D-aspartate (NMDA) receptor hypofunction. These patients also exhibit deficits in auditory sensory processing that manifests as impaired mismatch negativity (MMN), which is an auditory evoked potential (AEP) component related to NMDA receptor function. N-acetyl-cysteine (NAC), a glutathione precursor, was administered to patients to determine whether increased levels of brain glutathione would improve MMN and by extension NMDA function. A randomized, double-blind, cross-over protocol was conducted, entailing the administration of NAC (2 g/day) for 60 days and then placebo for another 60 days (or vice versa). 128-channel AEPs were recorded during a frequency oddball discrimination task at protocol onset, at the point of cross-over, and at the end of the study. At the onset of the protocol, the MMN of patients was significantly impaired compared to sex- and age- matched healthy controls (p=0.003), without any evidence of concomitant P300 component deficits. Treatment with NAC significantly improved MMN generation compared with placebo (p=0.025) without any measurable effects on the P300 component. MMN improvement was observed in the absence of robust changes in assessments of clinical severity, though the latter was observed in a larger and more prolonged clinical study. This pattern suggests that MMN enhancement may precede changes to indices of clinical severity, highlighting the possible utility AEPs as a biomarker of treatment efficacy. The improvement of this functional marker may indicate an important pathway towards new therapeutic strategies that target glutathione dysregulation in schizophrenia.

A glutathione precursor, N-acetyl-cysteine, modulates mismatch negativity generation in schizophrenia patients

Schizophrenia patients exhibit deficits in low-level processing, including pitch discrimination. This deficiency manifests in auditory evoked potentials (AEPs) as an impaired mismatch negativity (MMN), an electrophysiological response to infrequent target stimuli interspersed among frequent standard stimuli that typically peaks ~100ms post-stimulus onset. NMDA receptor antagonists have been shown to block MMN generation in both animals and humans, and NMDA dysfunction has been linked to the underlying pathophysiology of schizophrenia. A parallel line of evidence indicates that glutathione (GSH) regulation is perturbed in schizophrenia patients at the gene, protein and functional levels (Tosic et al., 2006). This GSH dysregulation leads to NMDA receptors' hypofunction through interaction with their redox site (Steullet et al., 2006). The present study aimed to modulate GSH levels in schizophrenia patients and assessed the effects of such a modulation on MMN generation mechanisms. N-acetyl-cysteine (NAC), a GSH precursor, was administered to schizophrenia patients, using a double-blind cross-over protocol. One group received NAC (2g/day) for 60 days and then placebo for another 60 days, and vice-versa for the second group. AEPs from patients were recorded at the onset of the protocol, at the point of cross-over, and at the end of the study. Participants were instructed to manually respond to target stimuli (2kHz pure tones occurring 20% of the time among 1kHz pure tones). Analyses of AEPs recorded at protocol onset indicated that patients (n=11) were significantly impaired in generating the MMN relative to age-matched controls (n=11). Specifically, the global field power (GFP), an index of AEP magnitude, was measured over the 70- 155ms post-stimulus interval and submitted to an analysis of variance (ANOVA). There was a significant interaction between population and stimulus frequency, indicating impaired MMN generation in patients at protocol onset. Analyses of AEPs recorded during administration of NAC (n=7) versus placebo (n=7) revealed the efficacy of this GSH precursor in modulating MMN generation mechanisms. ANOVA of GFP over the 70- 155ms post-stimulus interval, using stimulus frequency and treatment as within-participants variables, revealed a significant interaction and indicated that NAC can ameliorate MMN generation. We discuss these results in terms of potential therapeutic strategies for schizophrenia.

Changes of beta-amyloid precursor protein splice patterns in brain cell aggregate cultures.

The splice pattern of beta-amyloid precursor protein (beta-APP) has been studied in a variety of neuronal and glial cells and in brain cell aggregate cultures by the polymerase chain reaction (PCR). The brain-typical pattern, in which beta-APP695 is the dominant form, has been found only in aggregate cultures but not in any of the other cell types including neuronal cell lines. Selective elimination of glial cells from aggregates resulted in increased quantities of beta-APP695, whereas removal of neurons led to a reduction of beta-APP695 and to an elevation of beta-APP751 and beta-APP770. This shift of splice pattern was not observed in cocultures of the neuronal cell line PC 12 with primary astrocytes combined in a variety of cellular ratios. Blood serum, which is an essential component of these cultures, tested on aggregates, did not reduce the amount of beta-APP695 or have any marked effects on splice patterns generally. From these results it is concluded that investigations on brain-typical splicing of beta-APP require primary neurons. Neuronal cell lines may be no suitable model systems. Splicing events favoring production of beta-APP695 may mark an important, very early step of amyloid formation in the brain.

C/EBPbeta couples dopamine signalling to substance P precursor gene expression in striatal neurones.

Dopamine-induced changes in striatal gene expression are thought to play an important role in drug addiction and compulsive behaviour. In this study we report that dopamine induces the expression of the transcription factor CCAAT/Enhancer Binding Protein beta (C/EBP)-beta in primary cultures of striatal neurones. We identified the preprotachykinin-A (PPT-A) gene coding for substance P and neurokinin-A as a potential target gene of C/EBPbeta. We demonstrated that C/EBPbeta physically interacts with an element of the PPT-A promoter, thereby facilitating substance P precursor gene transcription. The regulation of PPT-A gene by C/EBPbeta could subserve many important physiological processes involving substance P, such as nociception, neurogenic inflammation and addiction. Given that substance P is known to increase dopamine signalling in the striatum and, in turn, dopamine increases substance P expression in medium spiny neurones, our results implicate C/EBPbeta in a positive feedback loop, changes of which might contribute to the development of drug addiction.

Precursor uptake assays and metabolic analyses in isolated tomato fruit chromoplasts

Background Carotenoids are the most widespread group of pigments found in nature. In addition to their role in the physiology of the plant, carotenoids also have nutritional relevance as their incorporation in the human diet provides health benefits. In non-photosynthetic tissues, carotenoids are synthesized and stored in specialized plastids called chromoplasts. At present very little is known about the origin of the metabolic precursors and cofactors required to sustain the high rate of carotenoid biosynthesis in these plastids. Recent proteomic data have revealed a number of biochemical and metabolic processes potentially operating in fruit chromoplasts. However, considering that chloroplast to chromoplast differentiation is a very rapid process during fruit ripening, there is the possibility that some of the proteins identified in the proteomic analysis could represent remnants no longer having a functional role in chromoplasts. Therefore, experimental validation is necessary to prove whether these predicted processes are actually operative in chromoplasts. Results A method has been established for high-yield purification of tomato fruit chromoplasts suitable for metabolic studies. Radiolabeled precursors were efficiently incorporated and further metabolized in isolated chromoplast. Analysis of labeled lipophilic compounds has revealed that lipid biosynthesis is a very efficient process in chromoplasts, while the relatively low incorporation levels found in carotenoids suggest that lipid production may represent a competing pathway for carotenoid biosynthesis. Malate and pyruvate are efficiently converted into acetyl-CoA, in agreement with the active operation of the malic enzyme and the pyruvate dehydrogenase complex in the chromoplast. Our results have also shown that isolated chromoplasts can actively sustain anabolic processes without the exogenous supply of ATP, thus suggesting that these organelles may generate this energetic cofactor in an autonomous way. Conclusions We have set up a method for high yield purification of intact tomato fruit chromoplasts suitable for precursor uptake assays and metabolic analyses. Using targeted radiolabeled precursors we have been able to unravel novel biochemical and metabolic aspects related with carotenoid and lipid biosynthesis in tomato fruit chromoplasts. The reported chromoplast system could represent a valuable platform to address the validation and characterization of functional processes predicted from recent transcriptomic and proteomic data.

Rapid transgene expression in multiple precursor cell types of adult rat subventricular zone mediated by adeno-associated type 1 vectors.

Abstract The adult rat brain subventricular zone (SVZ) contains proliferative precursors that migrate to the olfactory bulb (OB) and differentiate into mature neurons. Recruitment of precursors constitutes a potential avenue for brain repair. We have investigated the kinetics and cellular specificity of transgene expression mediated by AAV2/1 vectors (i.e., adeno-associated virus type 2 pseudotyped with AAV1 capsid) in the SVZ. Self-complementary (sc) and single-stranded (ss) AAV2/1 vectors mediated efficient GFP expression, respectively, at 17 and 24 hr postinjection. Transgene expression was efficient in all the rapidly proliferating cells types, that is, Mash1(+) precursors (30% of the GFP(+) cells), Dlx2(+) neuronal progenitors (55%), Olig2(+) oligodendrocyte progenitors (35%), and doublecortin-positive (Dcx(+)) migrating cells (40%), but not in the slowly proliferating glial fibrillary acidic protein-positive (GFAP(+)) neural stem cell pool (5%). Because cell cycle arrest by wild-type and recombinant AAV has been described in primary cultures, we examined SVZ proliferative activity after vector injection. Indeed, cell proliferation was reduced immediately after vector injection but was normal after 1 month. In contrast, migration and differentiation of GFP(+) precursors were unaltered. Indeed, the proportion of Dcx(+) cells was similar in the injected and contralateral hemispheres. Furthermore, 1 month after vector injection into the SVZ, GFP(+) cells, found, as expected, in the OB granular cell layer, were mature GABAergic neurons. In conclusion, the rapid and efficient transgene expression in SVZ neural precursors mediated by scAAV2/1 vectors underlines their potential usefulness for brain repair via recruitment of immature cells. The observed transient precursor proliferation inhibition, not affecting their migration and differentiation, will likely not compromise this strategy.