Demyelination patterns in a mathematical model of multiple sclerosis.

In this paper we derive a reaction-diffusion-chemotaxis model for the dynamics of multiple sclerosis. We focus on the early inflammatory phase of the disease characterized by activated local microglia, with the recruitment of a systemically activated immune response, and by oligodendrocyte apoptosis. The model consists of three equations describing the evolution of macrophages, cytokine and apoptotic oligodendrocytes. The main driving mechanism is the chemotactic motion of macrophages in response to a chemical gradient provided by the cytokines. Our model generalizes the system proposed by Calvez and Khonsari (Math Comput Model 47(7-8):726-742, 2008) and Khonsari and Calvez (PLos ONE 2(1):e150, 2007) to describe Baló's sclerosis, a rare and aggressive form of multiple sclerosis. We use a combination of analytical and numerical approaches to show the formation of different demyelinating patterns. In particular, a Turing instability analysis demonstrates the existence of a threshold value for the chemotactic coefficient above which stationary structures develop. In the case of subcritical transition to the patterned state, the numerical investigations performed on a 1-dimensional domain show the existence, far from the bifurcation, of complex spatio-temporal dynamics coexisting with the Turing pattern. On a 2-dimensional domain the proposed model supports the emergence of different demyelination patterns: localized areas of apoptotic oligodendrocytes, which closely fit existing MRI findings on the active MS lesion during acute relapses; concentric rings, typical of Baló's sclerosis; small clusters of activated microglia in absence of oligodendrocytes apoptosis, observed in the pathology of preactive lesions.

Propofol/alfentanil and propofol/ketamine procedural sedation in children with acute lymphoblastic leukaemia: safety, efficacy and their correlation with pain neuromediator expression.

Invasive procedures, such as the lumbar puncture, can cause anxiety and pain in children undergoing treatment for acute lymphoblastic leukaemia (ALL). We investigated the safety and efficacy of two different protocols for analgo-sedation in 20 children with ALL undergoing lumbar puncture. We have conducted a prospective, cross-over study. Protocol A was composed of an association between propofol and alfentanil. Protocol B consisted in the combination of propofol and ketamine. We also evaluated the levels of nerve growth factor, substance P and enkephalins in the cerebrospinal fluid of these patients. All patients showed a satisfactory sedation and analgesia. We found a statistically significant difference of vital parameters between protocol A and protocol B, while there were no significant differences between sedation scores and the other parameters evaluated. Patients in protocol A showed a higher incidence of major side effects, such as respiratory depression. Pain neuromediator levels did not show any statistical difference between the two groups. This study shows that both protocols are effective to obtain a good sedation and analgesia in children with ALL undergoing lumbar puncture, but the association between propofol and ketamine appears to be safer due to the lower incidence of side effects.

Cross-diffusion-induced subharmonic spatial resonances in a predator-prey system.

In this paper we investigate the complex dynamics originated by a cross-diffusion-induced subharmonic destabilization of the fundamental subcritical Turing mode in a predator-prey reaction-diffusion system. The model we consider consists of a two-species Lotka-Volterra system with linear diffusion and a nonlinear cross-diffusion term in the predator equation. The taxis term in the search strategy of the predator is responsible for the onset of complex dynamics. In fact, our model does not exhibit any Hopf or wave instability, and on the basis of the linear analysis one should only expect stationary patterns; nevertheless, the presence of the nonlinear cross-diffusion term is able to induce a secondary instability: due to a subharmonic spatial resonance, the stationary primary branch bifurcates to an out-of-phase oscillating solution. Noticeably, the strong resonance between the harmonic and the subharmonic is able to generate the oscillating pattern albeit the subharmonic is below criticality. We show that, as the control parameter is varied, the oscillating solution (subT mode) can undergo a sequence of secondary instabilities, generating a transition toward chaotic dynamics. Finally, we investigate the emergence of subT-mode solutions on two-dimensional domains: when the fundamental mode describes a square pattern, subharmonic resonance originates oscillating square patterns. In the case of subcritical Turing hexagon solutions, the internal interactions with a subharmonic mode are able to generate the so-called "twinkling-eyes" pattern.

A cheap protocol for colour measure and for diagnostic in planning a cultural heritage restoration. Case study: main façade of Palazzo Governi (Cagliari, Sardinia, Italy).

Due to the bad state of conservation, "Palazzo Governi", a seventeenth-century building located in the old town district of "Stampace" in Cagliari (Sardinia, Italy), was subjected to restoration. Thus, according to the Italian Law n. 1089, the main façade colour must be reproduced, and therefore, its identification was required. The available samples looked fairly degraded, in particular as an easy plaster to crumble; so, some other analyses able to identify the degradation cause were performed. Two different approaches were adopted to attain the first goal, the visual colour assessment by a sensory panel (subjective) and the instrumental measurement by colorimetry (objective). Ion chromatography and inductively coupled plasma-optical emission spectroscopy analyses, as well as conductivity and pH measurements, were performed to evaluate the presence of water-soluble salts inside the plaster, as possible cause of degradation; the binder/aggregate ratio was also evaluated. A full mineralogical and petrographic characterisation of the materials constituting the samples, as well as the identification of their stratigraphy and some other morphologic and structural features suitable to highlight eventual forms of degradation, were performed by optical microscopy. Scanning electron microscopy coupled to X-ray microanalysis was been also used in order to confirm and/or to integrate data obtained by optical microscopy. The samples have been compared with two samples coming from two other buildings, also located in Sardinia, that looked in good conservation state. The results evidenced that the causes of degradation come from a high salt (especially sulphate) content and a scarce presence of binder in the plaster that can be imputed to a wrong initial composition and/ or to a leaching by acidic rain.

A microclimate study on hypogea environments of ancient roman building.

Roman hypogea, vernacular settlements or crypts, are underground places characterised by specific and unique challenges (RH<90% and almost constant temperature throughout the whole year) related to their relative isolation from the outdoor environment. These sites often require adequate monitoring tools providing complete environmental information in order to carry out appropriate strategies for scheduling routine maintenance and designing suitable layouts for their preservation. In this work we present the results of a carefully planned thermo-hygrometric monitoring campaign conducted in a peculiar Roman building (130CE), the "Casa di Diana" Mithraeum, sited in Ostia Antica (archaeological site, Rome-Italy), with the aim of characterising the indoor environment as the structure suffers of several conservation problems (biocolonisation, efflorescences, evaporating and condensing cycle for wall-building materials). The campaign involving multipoint continuous measurement was carefully planned to better describe this micro-clime. In addition to underground environmental data available in literature, we have also performed, as a checkpoint control, a thermo-hygrometric monitoring campaign in the "Terme di Mitra" Hypogeum, a few meters from the "Casa di Diana". The recorded data was analysed by multivariate statistical and chemometric analyses. The results brought to light the presence of different microclimates (three areas) within a single Mithraeum: a room (pre-Mithraeum) and an area (Mithraeum: 2-4m) present a thermo-hygrometric environmental behaviour in accordance with a semi-confined environment, another area (Mithraeum: 1-2m) behaves accordingly with underground environments (although it cannot be described as such), and the last area (Mithraeum: 0-1m) where was recording RH values close to saturation (96-99%), associated with non-ventilated areas where the rising damp is "held" and not dispersed, describing an own micro-clime, comparable to a "small greenhouse". This study has allowed to identify some critical areas in view of planning future conservation solutions, without exporting the artefacts kept inside.

Dexamethasone-dependent modulation of human lymphoblastoid B cell line through sphingosine production.

The relationship between dexamethasone-dependent changes in intracellular sphingosine levels, energy and phospholipid metabolism have been investigated by 31P-NMR spectroscopy and high-performance liquid chromatography. The cellular functions have been evaluated by cellular growth and immunoglobulin M secretion (IgM). Significant increases in intracellular phosphorylcholine (PCho), extracellular choline (Cho), and endogenous sphingosine levels were observed only at 30 min incubation with dexamethasone. These results confirmed a sphingosine-dependent hydrolysis of choline-linked phospholipids (Miccheli, A., Ricciolini, R., Piccolella, E., Delfini, M. and Conti, F. (1991) Biochim. Biophys. Acta 1093, 29-35). Furthermore, no significant variations were evidenced at hours 1, 2, 6 and 18 of incubation. Dexamethasone causes an inhibition of cellular growth and IgM secretion as well as the sphingosine treatment. The results suggest that the effect of dexamethasone may be mediated by endogenous sphingosine production in Epstein-Barr virus transformed B lymphocytes.

Evaluation of the inhibiting effects from exposure to microwaves on the respiratory activity of yeast cells or on enzyme activity.

Microwaves are used in medical applications, so their eventual toxicity effects must be carefully evaluated. An integral toxicity test, based on the monitoring of the respiratory activity of yeast cells, is proposed to evaluate the damage from microwave exposure. Different exposure times and microwave powers were considered. On supposing that the damages occur at enzymatic levels, the inhibiting effects of microwave exposure on two enzymes (glucose oxidase (GOD) and superoxide dismutase (SOD)), assumed like models as present in the human organism, was evaluated.

A new assay for choline-containing phospholipids in amniotic fluid by an enzyme sensor.

A new rapid and direct method for the determination of choline-containing phospholipids in the amniotic fluid is proposed. The determination is performed by an amperometric-enzymatic method. The correlation with an enzymatic-spectrophotometric method, already published, is also considered.

The brain amino acid pattern in experimental coma due to phenytoin in guinea pigs.

An experimental study was carried out on 50 guinea pigs to evaluate the amino acid pattern in the whole brain after a toxic dose of phenytoin (1 g . kg-1 body wt). One group of 25 guinea pigs was treated with the drug which made them comatose, and their brains removed by craniotomy and frozen in liquid nitrogen; 25 guinea pigs were used as a control group. The brain amino acid pattern was determined by ion-exchange chromatography. All the amino acids, except threonine and methionine, decreased. Hypotheses about the particular cerebral metabolic pathways involved are discussed.

The amino acid cerebral pool after toxic doses of lidocaine and mexiletine. An experimental study on guinea pigs.

Lidocaine and Mexiletine are two anti-arrhythmic drugs which when administered in toxic doses cause alterations in the central nervous system (convulsions, tremors, coma). An experimental study was carried out to clarify some neurological side-effects caused by these two drugs, by studying the variations of the brain amino acid pool. With Lidocaine one can observe an increase of phenyl-alanine and tyrosine, a decrease of glycine, GABA, alanine, aspartate and glutamate, while taurine and ammonia showed no significant changes. After Mexiletine one can observe an increase of ammonia, a decrease of GABA, glutamine, glycine and alanine, while glutamate, taurine, phenyl-alanine and tyrosine remain within normal values. In conclusion, on the basis of the data obtained by comparing the two drugs, one could say that Lidocaine has a greater interference on the catecholaminic precursors which are little influenced by Mexiletine. For the rest, the data obtained are practically super- imposable .

The effect of organic solvent properties on the response of a tyrosinase enzyme sensor.

The use of an enzyme tyrosinase sensor capable of being employed in non aqueous media represents a good opportunity to investigate the effects of the organic solvent on enzyme activity. Six different solvents are considered (n-heptane, n-hexane, n-pentane, toluene, chloroform, acetonitrile) and two properties of these solvents are studied in particular, i.e. hydrophobicity (as log P) and dielectric constant, taking into account their influence on sensor response. Results are generally in agreement with those found by other authors, who determined the behaviour of the enzyme activity as a function of organic solvents using different methods.

Tyrosinase biosensor response as a function of physical properties of organic solvents.

The main aim was to investigate the possibility of developing a fast, easily produced biosensor capable of being used in non-aqueous solvents such as n-hexane, chloroform, mixtures thereof and water-saturated chloroform. The research also provided an experimental confirmation of several concepts, described in the literature, concerning enzymatic activity in different types of non-aqueous solvents. The results are decidedly encouraging as regards future possible uses of this sensor to determine soluble substances in non-aqueous solvents.

Further development of catalase, tyrosinase and glucose oxidase based organic phase enzyme electrode response as a function of organic solvent properties.

Using three enzyme sensors (tyrosinase, catalase and glucose oxidase), capable of functioning also in non-aqueous solvents, we found new correlations between classical indicators, e.g. the log P value of several organic solvents and new empirical indicators such as ;maximum current variation' (MCV) and above all the ;current variation rate' (CVR), the values of which may be monitored with the biosensor considered dipping directly into the organic solvent. The trend of the immobilised specific activity of the tyrosinase enzyme dipping into different organic solvents was evaluated and compared with that determined by the spectrophotometric method. Lastly, an investigation was performed to experimentally verify the relation between hydrophobicity of the solvent and its ability to draw back the water from the enzyme microenvironment using the Karl Fischer method and thermogravimetric analysis to estimate the residual water in the enzyme microenvironment after having treated the enzyme with the organic solvent, then allowing it to dry.

An algal biosensor for the monitoring of water toxicity in estuarine environments.

An algal biosensor for toxicity assessment of estuarine waters is proposed. The sensor was obtained by coupling a suited algal bioreceptor (the cyanobacterium Spirulina subsalsa) to an amperometric gas diffusion electrode. The analytical device allows the monitoring of the evolution of photosynthetic O2 and the detection of alterations due to toxic effects caused by environmental pollutants present in the medium. Four chemical species representative of three main different classes of pollutants (heavy metals, triazinic herbicides, carbamate insecticides) were tested at different concentrations using a standardized natural water as experimental medium. In all the cases a toxic response was detected (i.e. a dose-related inhibition of photosynthetic activity was recorded) with good reproducibility.

Analysis of L-dopa in pharmaceutical preparations and of total phenols content in urine by means of an enzyme-amperometric sensor.

An enzyme-amperometric method is proposed for the analysis of total phenols and L-dopa; the method is based on the enzyme tyrosinase, which is immobilized in a Nylon membrane and coupled to an oxygen gas-diffusion amperometric electrode. The method was applied to the determination of total phenols in urine and to L-dopa in formulations and was evaluated as a promising alternative to currently adopted methods, e.g. to a classical spectrophotometric technique, chosen as a reference method.

Analytical comparison of an enzyme-amperometric method for chlorocresol determination in ointments with colorimetry and liquid chromatography.

The direct determination of chlorocresol in n-hexane extracts of commercial ointments was successfully performed using an enzyme-amperometric probe for analysis of phenols and working in previously characterized and optimized non-aqueous solvents. The analytical data obtained were compared with those found by using classical HPLC or chemical spectrophotometric method for determination of phenols.

Aspartate analysis in formulations using a new enzyme sensor.

A biosensor has been developed for the purpose of directly analysing aspartate in pharmaceutical formulations and aspartame in sweeteners. This biosensor consists of an ammonia-sensitive gas-diffusion electrode and the enzyme L-aspartase immobilized by means of polyazetidine on a dialysis membrane.

A new salicylate ISFET for the determination of salicylic and acetylsalicylic acid in drugs.

A salicylate ISFET for the analysis of salicylic and acetylsalicylic acid in drugs is described. It is based on a salicylate ion selective membrane coated on the surface of the Si3N4 gate of the FET. The sensitive membrane consists of tetra-dodecylammonium salicylate, polyvinyl chloride and a proper plasticizer. The linearity range of the sensor is 5 x 10(-5)-1.5 x 10(-2) M for the salicylic acid, and 7 x 10(-5)-1.5 x 10(-2) M for the acetylsalicylic acid, respectively. The detection limit for the two compounds is 5 x 10(-5) M while the response time is < or = 20 s. The effect of pH and different interfering ions was also studied. The sensor was used to analyse the content of acetylsalicylic and salicylic acid in some drugs, and the accuracy of the method was evaluated through recovery tests. The results obtained with this method are well correlated either with those obtained with a classical ISE employing the same sensitive membrane or with the classical volumetric method.

Hydrogen peroxide determination in pharmaceutical formulations and cosmetics using a new catalase biosensor.

The possibility of evaluating the content of hydrogen peroxide in several authentic matrices, such as cosmetic and pharmaceutical formulations, was studied. A new catalase biosensor fabricated using an amperometric gas-diffusion oxygen sensor as electrochemical transducer and the catalase enzyme immobilized in kappa-carrageenan gel and capable of operating in both aqueous and non aqueous solvents was developed and tested for this purpose. Creams, emulsions and disinfectant solutions were analysed. To this end, a preliminary check was needed to establish the best conditions to analyse these matrices; the choice of solvent was one of the most important points studied. The solvents considered included dioxane, water-dioxane mixtures, water saturated chloroform and aqueous solutions. The different solubility properties of the matrices analysed were taken into account.

Analysis of lecithin in pharmaceutical products and diet integrators using a new biosensor operating directly in non aqueous solvent.

One of the first examples of a bienzymatic organic phase enzyme electrode (OPEE) is described. It was obtained using two enzymes (phospholipase D and choline oxidase), both immobilised in kappa-Carrageenan gel and, as electrochemical transducer, an amperometric gas diffusion electrode for oxygen. The response of the biosensor was recorded and its sensitivity, linearity range, response time evaluated. Lastly drugs and diet products containing lecithin were analysed using the new biosensor device working in an organic mixture.