Halpha surface photometry of galaxies in the Virgo cluster. IV: the current star formation in nearby clusters of galaxies

Halpha+[NII] imaging observations of 369 late-type galaxies in the Virgo cluster and in the Coma/A1367 supercluster are analyzed. They constitute an optically selected sample (m_p<16.0) observed with 60% c.a. completeness.These observations provide us with the current (T<10^7 yrs) star formation properties of galaxies. The expected decrease of the star formation rate (SFR),as traced by the Halpha E.W., with decreasing clustercentric projected distance is found only when galaxies brighter than M_p=-19.5 are considered. We also include in our analysis Near Infrared data, providing us with informations on the old (T>10^9yrs) stars. Put together, the young and the old stellar indicators give the ratio of currently formed stars over the stars formed in the past, or "birthrate" parameter b. We also determine the "global gas content" combining HI with CO observations. We define the "gas deficiency" parameter as the logarithmic difference between the gas content of isolated galaxies of a given Hubble type and the measured gas content.For the isolated objects we find that b decreases with increasing NIR luminosity. The gas-deficient objects, primarily members to the Virgo cluster, have their birthrate significantly lower than the isolated objects with normal gas content and of similar NIR luminosity. This indicates that the current star formation is regulated by the gaseous content of spirals.Whatever mechanism (most plausibly ram-pressure stripping) is responsible for the pattern of gas deficiency observed in spiral galaxies members to rich clusters, it also produces the observed quenching of the current star formation.Comment: 22 pages,14 figures,3 figures available in jpeg format.To be published in A&

Meta-analysis of cancer incidence in children born after assisted reproductive technologies

A meta-analysis was performed on 11 cohort studies of Assisted Reproductive Technologies (ART) and subsequent childhood cancer, published up to February 2005, which reported comparable, nonoverlapping data, and then restricted to eight studies which presented a similar research design. The overall Standardised Incidence Ratio was 1.33 (95% CI 0.62–2.85), and 0.77 (95% CI 0.41–1.42) when the analysis was restricted to eight studies. No evidence of publication bias was observed for the overall analysis. The data are consistent with a lack of increase in risk of childhood cancer, though the amount of data on ART and cancer is still limited; larger multicentric studies as well as a pooled analysis on the available data are warranted

AEROBIC AND ANAEROBIC METABOLISM DURING LOCOMOTION WITH TWO DIFFERENT WHEELCHAIR TYPES

Wheelchair design is extremely important in order to improve efficiency of locomotion and reduce physical stress in subjects whose muscular and cardiopulmonary fitness are impaired. Purpose of this study was to evaluate the effect of different wheelchair design on the aerobic and anaerobic metabolism during locomotion at different speeds in paraplegic subjects. The experiments were carried out on a group of 5 male paraplegic subjects (25 ±3 years; body weight 65±7kg) during locomotion on a roller ergometer (Sopur, Ergotronic mod.) at 3-4 different speeds from 2 to 9 km/h. At each speed oxygen consumption and heart rate were determined after at least 6 min of exercise. Lactic acid (LA) venous blood concentration was evaluated before and at the 5th min of recovery and lactate production was calculated. The oxygen equivalent of LA was assumed to be 3.15ml O2 per kg body weight for an increase of blood LA of 1 mmol/L. For each subject the test was repeated using two different types of daily use active wheelchairs: type A., foldable, 13.95kg; type B, demountable, 13.35kg. The main difference in size was in the horizontal location of the wheel axle, in seat height and in handrim diameter. Results indicate that: a) oxygen consumption increased linearly with speed being 2050±350ml/min and 1780±270ml/min at 9km/h for wheelchair type A and B, respectively; b)lactic acid concentrations were significantly higher, at a given speed, while using wheelchair type A than B (at 9km/h; 7.4±1.5 mmol/l and 6.0±1.6 mmol/l, respectively),c) the total energy required , aerobic and anaerobic, increased linearly with speed and was 15-20% higher with wheelchair type A than B at all speeds; d) the energy cost of locomotion at a given speed was in the 15-25% range higher for wheelchair A than B; e) at corresponding oxygen uptake, heart rate and pulmonary ventilation were not different with the two wheelchair types. The main results of this study concern the large difference existing in the energy cost of locomotion and in the lactate production in the same subject when two different wheelchairs, even if apparently similar are used. In particular the much higher lactate production suggests that wheelchair design affects the limb and trunk movements in such a way that the metabolism of some muscle group requires a greater participation of anaerobic mechanism of energy supply, this leading to early onset of muscular fatigue. Further studies, in particular the combined biomechanical analysis of user and wheelchair during locomotion are required to increase the optimum fitting of wheelchair –user interface

Optical spectroscopy of galaxies in the direction of the Virgo cluster

Optical spectroscopy of 76 galaxies, 48 of which are projected in the direction of the Virgo cluster and 28 onto the Coma-A1367 supercluster, is reported. Adding these new measurements to those found in the literature, the redshift completeness in the Virgo region becomes 92% at B_T<=16.0 and 68% at B_T<=18.0. The one of CGCG galaxies in the direction of the Coma-A1367 supercluster becomes 98%. The Virgo cluster membership estimates obtained on morphological grounds by Binggeli et al. (1985) are confirmed in all cases. However, several "possible members" classified as BCD (if in the cluster) are found instead to be giant emission-line galaxies in the background of the Virgo clusterComment: LaTeX, 8 pages, 5 figures, accepted for pubblication in A&

Erasing Sensorimotor Memories via PKMζ Inhibition

Sensorimotor cortex has a role in procedural learning. Previous studies suggested that this learning is subserved by long-term potentiation (LTP), which is in turn maintained by the persistently active kinase, protein kinase Mzeta (PKMζ). Whereas the role of PKMζ in animal models of declarative knowledge is established, its effect on procedural knowledge is not well understood. Here we show that PKMζ inhibition, via injection of zeta inhibitory peptide (ZIP) into the rat sensorimotor cortex, disrupts sensorimotor memories for a skilled reaching task even after several weeks of training. The rate of relearning the task after the memory disruption by ZIP was indistinguishable from the rate of initial learning, suggesting no significant savings after the memory loss. These results indicate a shared molecular mechanism of storage for declarative and procedural forms of memory

Antibody binding modulates conformational exchange in domain III of dengue virus E protein

Domain III of dengue virus E protein (DIII) participates in the recognition of cell receptors and in structural rearrangements required for membrane fusion and ultimately viral infection; furthermore, it contains epitopes for neutralizing antibodies and has been considered a potential vaccination agent. In this work, we addressed various structural aspects of DIII and their relevance for both the dengue virus infection mechanism and antibody recognition. We provided a dynamic description of DIII at physiological and endosomal pHs and in complex with the neutralizing human antibody DV32.6. We observed conformational exchange in the isolated DIII, in regions important for the packing of E protein dimers on the virus surface. This conformational diversity is likely to facilitate the partial detachment of DIII from the other E protein domains, which is required to achieve fusion to the host cellular membranes and to expose the epitopes of many anti-DIII antibodies. A comparison of DIII of two dengue virus serotypes revealed many common features but also some possibly unexpected differences. Antibody binding to DIII of dengue virus serotype 4 attenuated the conformational exchange in the epitope region but, surprisingly, generated exchange in other parts of DIII through allosteric effects

The Self Model and the Conception of Biological Identity in Immunology

The self/non-self model, first proposed by F.M. Burnet, has dominated immunology for sixty years now. According to this model, any foreign element will trigger an immune reaction in an organism, whereas endogenous elements will not, in normal circumstances, induce an immune reaction. In this paper we show that the self/non-self model is no longer an appropriate explanation of experimental data in immunology, and that this inadequacy may be rooted in an excessively strong metaphysical conception of biological identity. We suggest that another hypothesis, one based on the notion of continuity, gives a better account of immune phenomena. Finally, we underscore the mapping between this metaphysical deflation from self to continuity in immunology and the philosophical debate between substantialism and empiricism about identity

Relative power and sample size analysis on gene expression profiling data

Background: With the increasing number of expression profiling technologies, researchers today are confronted with choosing the technology that has sufficient power with minimal sample size, in order to reduce cost and time. These depend on data variability, partly determined by sample type, preparation and processing. Objective measures that help experimental design, given own pilot data, are thus fundamental. Results: Relative power and sample size analysis were performed on two distinct data sets. The first set consisted of Affymetrix array data derived from a nutrigenomics experiment in which weak, intermediate and strong PPARα agonists were administered to wild-type and PPARα-null mice. Our analysis confirms the hierarchy of PPARα-activating compounds previously reported and the general idea that larger effect sizes positively contribute to the average power of the experiment. A simulation experiment was performed that mimicked the effect sizes seen in the first data set. The relative power was predicted but the estimates were slightly conservative. The second, more challenging, data set describes a microarray platform comparison study using hippocampal δC-doublecortin-like kinase transgenic mice that were compared to wild-type mice, which was combined with results from Solexa/Illumina deep sequencing runs. As expected, the choice of technology greatly influences the performance of the experiment. Solexa/Illumina deep sequencing has the highest overall power followed by the microarray platforms Agilent and Affymetrix. Interestingly, Solexa/Illumina deep sequencing displays comparable power across all intensity ranges, in contrast with microarray platforms that have decreased power in the low intensity range due to background noise. This means that deep sequencing technology is especially more powerful in dete

Occlusion of LTP-Like Plasticity in Human Primary Motor Cortex by Action Observation

Passive observation of motor actions induces cortical activity in the primary motor cortex (M1) of the onlooker, which could potentially contribute to motor learning. While recent studies report modulation of motor performance following action observation, the neurophysiological mechanism supporting these behavioral changes remains to be specifically defined. Here, we assessed whether the observation of a repetitive thumb movement – similarly to active motor practice – would inhibit subsequent long-term potentiation-like (LTP) plasticity induced by paired-associative stimulation (PAS). Before undergoing PAS, participants were asked to either 1) perform abductions of the right thumb as fast as possible; 2) passively observe someone else perform thumb abductions; or 3) passively observe a moving dot mimicking thumb movements. Motor evoked potentials (MEP) were used to assess cortical excitability before and after motor practice (or observation) and at two time points following PAS. Results show that, similarly to participants in the motor practice group, individuals observing repeated motor actions showed marked inhibition of PAS-induced LTP, while the “moving dot” group displayed the expected increase in MEP amplitude, despite differences in baseline excitability. Interestingly, LTP occlusion in the action-observation group was present even if no increase in cortical excitability or movement speed was observed following observation. These results suggest that mere observation of repeated hand actions is sufficient to induce LTP, despite the absence of motor learning