Neuronal Functional Connection Graphs among Multiple Areas of the Rat Somatosensory System during Spontaneous and Evoked Activities

Small-World Networks (SWNs) represent a fundamental model for the comprehension of many complex man-made and biological networks. In the central nervous system, SWN models have been shown to fit well both anatomical and functional maps at the macroscopic level. However, the functional microscopic level, where the nodes of a network are represented by single neurons, is still poorly understood. At this level, although recent evidences suggest that functional connection graphs exhibit small-world organization, it is not known whether and how these maps, potentially distributed in multiple brain regions, change across different conditions, such as spontaneous and stimulus-evoked activities. We addressed these questions by analyzing the data from simultaneous multi-array extracellular recordings in three brain regions of rats, diversely involved in somatosensory information processing: the ventropostero-lateral thalamic nuclei, the primary somatosensory cortex and the centro-median thalamic nuclei. From both spike and Local Field Potential (LFP) recordings, we estimated the functional connection graphs by using the Normalized Compression Similarity for spikes and the Phase Synchrony for LFPs. Then, by using graph-theoretical statistics, we characterized the functional topology both during spontaneous activity and sensory stimulation. Our main results show that: (i) spikes and LFPs show SWN organization during spontaneous activity; (ii) after stimulation onset, while substantial functional graph reconfigurations occur both in spike and LFPs, small-worldness is nonetheless preserved; (iii) the stimulus triggers a significant increase of inter-area LFP connections without modifying the topology of intra-area functional connections. Finally, investigating computationally the functional substrate that supports the observed phenomena, we found that (iv) the fundamental concept of cell assemblies, transient groups of activating neurons, can be described by small-world networks. Our results suggest that activity of neurons from multiple areas of the rat somatosensory system contributes to the integration of local computations arisen in distributed functional cell assemblies according to the principles of SWNs.     

In silico pKa Prediction and ADME Profiling

Improving the ADME profile of drug candidates is a critical step in lead optimization, and because pK_a affects most ADME properties such as lipophilicity, solubility, and metabolism, it is extremely advantageous to predict pK_a in order to guide the design of new compounds. However, accurately (<0.5 log units) predicting pK_a by empirical methods can be challenging especially for novel series, because of lack of knowledge on determinants of pK_a (steric effects, ring effects, H‐bonding, etc.), and because of limited experimental data on the effects of specific chemical groups on the ionization of an atom. To address these issues, we recently developed the computational package MoKa, which integrates graphical and command line tools designed for computational and medicinal chemists to predict the pK_a values of organic compounds. Here, we present the major issues considered when we developed MoKa, such as the accurate selection of training data, the fundamentals of the methodology (which has also been extended to predict protein pK_a), the treatment of multiprotic compounds, and the selection of the dominant tautomer for the calculation. Last, we illustrate some specific applications of MoKa to predict solubility, lipophilicity, and metabolism.     

Relationships among hemocytes, tunic cells, germ cells, and accessory cells in the colonial ascidian Botryllus schlosseri

Monoclonal antibodies were raised against hemocytes of the colonial ascidian Botryllus schlosseri as possible tools to study hemocyte differentiation. In this species, blood cells are involved in various biological functions, such as immunosurveillance, encapsulation of foreign bodies, metal accumulation, and allorecognition. The latter process drives the fusion or rejection of contacting colonies, according to whether they do or do not share at least one allele at the fusibility/histocompatibility (Fu/HC) locus. Hemocytes take part in the rejection reaction, which suggests that they express molecules, coded by the Fu/HC locus, on their surface. A homozygous colony at the Fu/HC locus was used to produce the antibodies, which were screened by immunocytochemistry on hemocyte monolayers, immunohistochemistry on colony paraffin sections, and immunoblotting on colony homogenates. Here, we report on one of the obtained antibodies (1D8), which recognized a surface epitope on hemocytes of the donor colony and other colonies, apparently in a manner specific to the Fu/HC genotype. It also labeled a single 80-kDa band in colony homogenates. In addition, it specifically recognized tunic cells, germ cells, and their accessory cells. These results strengthen the assumption of a close relationship among these types of cells and blood cells, and suggest a close relationship among the above cells, probably deriving from undifferentiated blood cells.     

Morpho-functional characterization of haemocytes of the compound ascidian Botrylloides leachi (Tunicata, Ascidiacea)

A morpho‐functional study of the colonial ascidian Botrylloides leachi haemocytes was carried out to propose their classification, relationships and specializations. This characterization was obtained by (i) investigations of both living and aldehyde‐fixed cells by light and electron microscopy; (ii) cytochemical and cytoenzymatic assays; (iii) lectin‐affinity assays; (iv) phagocytosis and haemagglutination assays; and (v) anti‐CD34 immunocytochemical assay for vertebrate haematopoietic stem cells. Results indicate that the haemoblast is a circulating stem cell and there are at least five haemocyte differentiation pathways, the last two of which have never been described in botryllids: (i) phagocytic line (hyaline amoebocytes and macrophage‐like cells) share ultrastructural features, the same hydrolytic enzymes and WGA lectin binding, and are involved in yeast phagocytosis and erythrocyte rosette formation; (ii) cytotoxic line (granular amoebocytes and morula cells) with vacuoles containing oxidative enzymes and polyphenolic substrates; (iii) vacuolated cell line (pigment cells and nephrocytes) involved in catabolite storage; (iv) compartment cell line (compartment amoebocytes and compartment cells) able to agglutinate erythrocytes and characterized by vacuoles with a moderately electron‐dense content, positive to arylsulphatase activity and binding DBA, UEA‐I, HPA lectins; and (v) granular cell line includes trophic cells, able to infiltrate the gut epithelium, showing a cytoplasm filled of PAS‐positive vacuoles with arylsulphatase, chloroacetylesterase and β‐glucuronidase activities.     

An insight of early PrP-E200K aggregation by combined molecular dynamics/fragment molecular orbital approaches

Unveiling the events leading to the formation of prion particles is a nowadays challenge in the field of neurochemistry. Pathogenic mutants of prion protein (PrP) are characterized by both an intrinsic tendency to aggregation and scrapie conversion propensity. However, the question about a possible correlation between these two events lasts still unanswered. Here, a multilayered computational workflow was employed to investigate structure, stability, and molecular interaction properties of a dimer of PrP^C-E200K, a well-known mutant of the PrP that represents a reduced model of early aggregates of this protein. Based on the combination of molecular dynamics and quantum mechanical approaches, this study provided for an in depth insight of PrP^C-E200K dimer in terms of residue-residue interactions. Assembly hypotheses for the early aggregation of PrP^C-E200K are paved and compared with PrP^Sc models reported in the literature to find a structural link between early and late (scrapie) aggregates of this protein.     

Expression of proopiomelanocortin-related peptides in human follicular fluid

In order to evaluate the expression of the opioid precursor proopiomelanocortin (POMC) in the ovarian follicle, we measured 6 of its main end-products in 23 follicular fluids. We coupled high performance liquid chromatography (HPLC) to specific radioimmunoassays. Seven follicles were immature (diameter less than 9 mm), 10 were obtained from superovulated patients during an in vitro fertilization-embryo transfer program (greater than 22 mm) and six were persistent follicles, collected during the luteal phase [15-31 mm, luteinized unruptured follicles (LUF)]. Follicular fluids were extracted by mean of Sep-pak cartridges and then purified by HPLC with a reverse-phase C-18 column eluted in a linear gradient with acetonitrile/0.01 M hydrochloric acid (from 18:82 to 40:60). Fractions were tested with specific antisera for ACTH (1-39), alpha-MSH, beta-lipotropin (beta-LPH), beta-endorphin (beta-EP) and gamma-endorphin (gamma-EP) immunoreactivities. No presence of beta-LPH, beta-EP and ACTH was confirmed, while gamma-EP, alpha-MSH and des-alpha-MSH were detected for the first time in follicular fluid. In every class of follicles shorter chain peptides predominate over their longer chain precursor. Immature follicles are characterized by the highest amounts of gamma-EP, ACTH, alpha-MSH and des-alpha-MSH if compared to superovulated and LUF. On the contrary, beta-EP amount was highest after superovulation. Apart from this finding, peptide levels in superovulated patients and LUF are similar.(ABSTRACT TRUNCATED AT 250 WORDS)     

First evidence of cell division in circulating haemocytes from the Manila clam Tapes philippinarum

In the present study, we report on haemocyte distribution, determined by a Coulter Counter, in the clam Tapes philippinarum. In addition, cytoskeleton components of haemocytes were examined using specific probes for F-actin and alpha-tubulin. The mean number of circulating haemocytes was 5 (x10(6))cells/ml haemolymph. Two main haemocyte populations were found in the haemolymph: small cells, 2-3microm in diameter and 10-100fl in volume; and large cells, 6-10microm in diameter and 150-400fl in volume. Analysis of the haemocyte cytoskeleton revealed bundles of actin filaments oriented according to the cell major axis, and microtubules radiating from the microtubule-organizing centre in proximity of the nucleus. Interestingly, mitotic spindles were also found radiating from the microtubule-organizing centres, located at the spindle poles (centrosomes) of undifferentiated cells. On the basis of both our previous findings regarding circulating stem cells (Cima, F., Matozzo, V., Marin, M.G., Ballarin, L., 2000. Haemocytes of the clam Tapes philippinarum (Adams & Reeve, 1850): morphofunctional characterisation. Fish Shellfish Immunol 10, 677-693) and new information from the present study, we suggest that haemoblasts are able to divide in the haemolymph of T. philippinarum. To our knowledge, this is the first report of mitotic spindles in circulating haemocytes from a bivalve species.     

Morphological and cytoenzymatic characterization of haemocytes of the venus clam Chamelea gallina

A morphological and enzymatic characterization of Chamelea gallina haemocytes was carried out as a prerequisite for further studies on venus clam immunobiology. Two main types of circulating haemocytes were identified (1) hyalinocytes (79.2%), agranular cells with a central nucleus surrounded by a little cytoplasm, and (2) granulocytes (16.5%), smaller granular cells with smaller nuclei. Small cells with a strongly basophilic nucleus and a thin layer of peripheral cytoplasm, probably undifferentiated blast cells (4.3%), were also observed. Both granulocytes and hyalinocytes can assume a spreading or round morphology. The enzymatic activities of haemocytes were also investigated. Some of the granulocytes and hyalinocytes were positive for hydrolytic enzymes, suggesting a role for these cells in phagocytosis; no oxidative enzymes were detected in C. gallina haemocytes. Granulocytes and hyalinocytes can easily adhere to the substratum and exhibit a low phagocytosis activity towards foreign particles (6.3%), whereas the fraction of cells containing ingested material significantly increased after pre-incubation of test particles with cell-free haemolymph, which suggests the presence of opsonin(s) in the haemolymph.