The patients' perspective on the perceived difficulties of dual-tasking: development and validation of the Dual-task Impact on Daily-living Activities Questionnaire (DIDA-Q).

BACKGROUND: Everyday-life activities often require performing dual tasks (DT), with consequent possible occurrence of motor-cognitive or motor-motor interference. This could reduce quality of life, in particular in people with neurological diseases. However, there is lack of validated tools to assess the patients' perspective on DT difficulties in this population. Therefore, we developed the Dual-task Impact on Daily-living Activities-Questionnaire (DIDA-Q) and tested its psychometric properties in people with multiple sclerosis (PwMS). METHODS: Items were generated based on existing scales, DT paradigms used in previous studies and the opinion of a multi-stakeholder group, including both experts and PwMS. Twenty DT constituted the preliminary version of the DIDA-Q which was administered to 230 PwMS. The psychometric properties of the scale were evaluated including internal consistency, validity and reliability. RESULTS: Nineteen items survived after exploratory factor analysis, showing a three-factor solution which identifies the components mostly contributing to DT perceived difficulty (i.e., balance and mobility, cognition and upper-limb ability). The DIDA-Q appropriately fits the graded response model, with first evaluations supporting internal consistency (Cronbach's alpha=0.95), validity (70% of the hypotheses for convergent and discriminant constructs confirmed) and reliability (intraclass correlation coefficients=0.95) of this tool. CONCLUSION: The DIDA-Q could be used in research and clinical settings to discriminate individuals with low vs. high cognitive-motor or motor-motor interference, and to develop and evaluate the efficacy of personalized DT rehabilitative treatments in PwMS.

Tinetti and Berg balance scales correlate with disability in hereditary peripheral neuropathies: a preliminary study.

BACKGROUND: The combination of distal muscle weakness, sensory defects and feet deformities leads to disequilibrium in patients affected by Charcot-Marie-Tooth (CMT) neuropathy. Studies relating the outcome of balance scales and clinical severity of CMT are lacking. AIM: To evaluate the accuracy of the Tinetti Balance scale (TBS) and Berg Balance scale (BBS) in identifying balance disorders and quantifying disease severity in CMT patients. DESIGN: Observational study. SETTING: University of Genoa-IRCCS AOU San Martino IST-Department of Neurology, Italy. POPULATION: Nineteen individuals with a diagnosis of CMT (12 females, 7 males, age 41.26±12.42). METHODS: All subjects underwent an evaluation with both TBS and BBS. Disability was quantified with CMT neuropathy score (CMTNS). Moreover, a complete neurophysiological study was performed. Distal lower limbs strength was evaluated with MRC scale. Pearson rank order correlation was used to determine the correlation between the scores on the two tests and to identify an eventual correlation between TBS or BBS and the CMTNS. RESULTS: Both scales showed a highly significant negative correlation with the CMTNS (r=-0.78, P<0.0005 and r=-0.77, P<0.001, respectively) and distal weakness on the anterior tibial muscles (AT) (TBS: AT left: r=0.65, P<0.005 and AT right: 0.59, P<0.01; BBS: AT left r=+0.71, P<0.001 and AT right r=+0.66, P<0.005). We found also a highly significant, positive correlation between the two different balance scales (r=+0.9, P<0.0001). CONCLUSION: TBS and BBS strongly correlate with disease disability and distal muscular weakness. CLINICAL REHABILITATION IMPACT: Both TBS and BBS may play a relevant role in the assessment of disability in patients affected by CMT. Further studies are needed to validate our results in a larger population.

Interactions of melatonin with mammalian mitochondria. Reducer of energy capacity and amplifier of permeability transition.

Melatonin, a metabolic product of the amino acid tryptophan, induces a dose-dependent energy drop correlated with a decrease in the oxidative phosphorylation process in isolated rat liver mitochondria. This effect involves a gradual decrease in the respiratory control index and significant alterations in the state 4/state 3 transition of membrane potential (ΔΨ). Melatonin, alone, does not affect the insulating properties of the inner membrane but, in the presence of supraphysiological Ca2+, induces a ΔΨ drop and colloid-osmotic mitochondrial swelling. These events are sensitive to cyclosporin A and the inhibitors of Ca2+ transport, indicative of the induction or amplification of the mitochondrial permeability transition. This phenomenon is triggered by oxidative stress induced by melatonin and Ca2+, with the generation of hydrogen peroxide and the consequent oxidation of sulfydryl groups, glutathione and pyridine nucleotides. In addition, melatonin, again in the presence of Ca2+, can also induce substantial release of cytochrome C and AIF (apoptosis-inducing factor), thus revealing its potential as a pro-apoptotic agent.

Complexation of cadmium and copper by fluvial humic matter and effects on their toxicity.

The effects of humic acids and fulvic acids isolated from the River Arno (Italy) on the bioavailability and toxicity of cadmium and copper were assessed in relation to changes in their speciation. Measurements of the complexing capacity of solutions containing these organic ligands were carried out by a titration procedure followed by DPASV and toxicity tests were carried out using lysosomes isolated from rat liver. The complexing capacity of the physiological medium containing about 13 mg/L of humic acids, expressed as ligand concentrations, was 0.30 and 0.072 micromol/L for cadmium and copper respectively; the corresponding conditional stability constants were 4.2 x 10(11) and 1.3 x 10(8) (mol/L)-1. The complexing capacities of the solution containing the same amount of fulvic acids were 0.33 and 0.164 micromol/L for cadmium and copper respectively, the conditional stability constants were 3.2 x 10(11) and 2.4 x 10(7) (mol/L)-1. The humic acids reduced the toxicity of cadmium by about 5 times: the EC50 changed from 4.4 to 20.4 micromol/L. The dose effect curve of copper presented a bi-sigmoid trend and two EC50 values can be determined: The EC50(1) in the presence of humic acids changed from 2.0 to 3.1 micromol/L, while the EC50(2) increased from 22.3 to 45.3 micromol/L. The fulvic acids reduced the cadmium toxicity by about the same amount as humic acids, from 4.4 to 18.6 micromol/L, but they had no effect on copper toxicity. Analysing the chemical speciation of cadmium and copper in the presence of humic components and under toxicity test conditions we can say that the appreciable decrease of EC50 is not related to changes in their speciation; we can hypothesize that this is due to different processes, as well as to blocking of the lysosomal membrane. On the basis of the shape of the dose-effect curves obtained for cadmium and copper respectively, we can say that the toxic effects of the two metals are different and we can hypothesize that copper could exercise its toxic activity by inhibiting the ATP-driven proton pump and the function of the Cl- selective channel.

Effect of metal complexes on thioredoxin reductase and the regulation of mitochondrial permeability conditions.

Gold(I) compounds such as auranofin, chloro(triethylphosphine) gold(I), and aurothiomalate act on mitochondrial functional parameters by determining an extensive permeability transition and a decrease of membrane potential. On the contrary, pyridine nucleotides and glutathione are not modified, whereas a slight but significant decrease of total thiols is apparent. The effect of gold(I) compounds is essentially referable to the inhibition, in the nanomolar range, of thioredoxin reductase activity and to an increase of hydrogen peroxide production. Metal ions and metal complexes (zinc and cadmium acetate, cisplatin, tributyltin) are also good inhibitors of thioredoxin reductase, although in the micromolar range, and in addition, they act as inducers of permeability transition and of membrane potential decrease. At variance with gold(I) compounds, which appear to work almost exclusively on thioredoxin reductase, metal ions and complexes are less specific, since they are active on different mitochondrial targets, including the respiratory chain.

Combined effect of propofol and GSNO on oxidative phosphorylation of isolated rat liver mitochondria.

Isolated rat liver mitochondria have been treated with the general anaesthetic propofol (2,6-diisopropylphenol, 200 microM) and the physiological NO donor nitrosoglutathione (GSNO, 200 or 250 microM). The efficiency of the oxidative phosphorylation has been evaluated by measuring the respiration and ATP synthesis rates and the behavior of transmembrane electrical potential. In mitochondria energized by succinate, the simultaneous presence of both propofol and GSNO gives rise to a synergic action in affecting the resting and the ADP-stimulated respiration, the respiratory control ratio, the ATP synthesis, and the formation and utilization of the electrochemical transmembrane potential.

The interaction of tributyllead with lysosomes from rat liver.

The interactions of tributyllead with lysosomes from rat liver have been studied. It results that the organometal compound induces a fast alkalinization in energized lysosomes. The interpretation is that the compound is a potent proton carrier. This function could explain the toxicity, in particular at neurological level of the compound.

The interactions of trialkyltin compounds with lysosomes from rat liver.

Interactions of two trialkyltin compounds with the lysosomes from a rat liver have been studied. It is shown that these compounds induce a fast alkalinisation in the matrix of energised lysosomes. The fast alkalinisation rate is similar to the one obtained with uncouplers of the oxidative phosphorylation. An identical effect has been obtained with lysosomes energised in a chloride-free medium. This supports the hypothesis that trialkyltin compounds behave not only as Cl-/OH- exchangers, but also as proton carriers in biological membranes. This result could explain the toxicity and in particular the neurotoxicity of trialkyltin compounds.

Lonidamine cytotoxicity: involvement of the lysosomal compartment.

Lonidamine (LND) was found to decrease significantly the pH gradient across intracellular compartments in Ehrlich ascites tumour cells. The effect was maximal in the range 0.2 - 0.3 mM LND, and was observed both in the presence of glucose - i.e. conditions in which a high bioenergetic status of the cells was maintained by glycolysis (due to a strong Crabtree effect in these cells) - and in the absence of glucose. Moreover the LND effect was also observed in the presence of bafilomycin, a specific inhibitor of the H+ -vacuolar ATP-ase. Based on these findings, we suggest that the LND effect on the proton gradient reflects an LND-induced increase in membrane proton conductance. The consequent impairment of intracellular proton gradients might be involved in the mechanism of action of LND, allowing drugs that are weak bases to accumulate preferentially in the cytoplasm and nucleus.

Effect of 2,6-diisopropylphenol and halogenated anesthetics on tetraphenylphosphonium uptake by rat brain synaptosomes: determination of membrane potential.

The effect of 2,6-diisopropylphenol (propofol) in comparison to that of the halogenated anesthetics enflurane, isoflurane, and halothane on tetrapenylphosphonium uptake by rat brain synaptosomes was studied. A direct method to separately measure the synaptosomal and the mitochondrial transmembrane potential by using the tetraphenylphosphonium cation (TPP+) was utilized. The latter is a lipophylic charged molecule which distributes between two compartments according to the transmembrane electrical potential in the presence or absence of 60 mM KCl as a synaptosomal membrane depolarizing agent. After previously reporting the damages induced by general anesthetics on isolated mitochondria, the aim of this paper was to study their possible action on the synaptosomal membrane potential and whether or not drugs concentrations damaging isolated mitochondria are also effective on synaptosomal mitochondria. The results indicated that, in the presence of glucose, mitochondria included in synaptosomes were able to maintain a transmembrane potential of 202+/-8 mV (mean +/- SD) while the synaptosomal membrane showed a potential of 78+/-8 mV (mean +/- SD). When anesthetic concentrations (0.6-1 mM propofol, 10-40 microM enflurane, 30-50 microM isoflurane, 8-15 microM halothane) that impair mitochondrial energy metabolism were used, the synaptosomal transmembrane potential was maintained and, in addition, a slight increase of the TPP+ taken up was observed as the anesthetic concentration was increased.

An in vitro study on the toxic effects of nonylphenols (NP) in mitochondria.

This paper is focused on alkylphenols, compounds which are formed by the biodegradation of polyethoxilatedalkylphenols detergents. Our experiments show that alkylphenols act not only as detergents, but also as uncouplers of the oxidative phosphorylation. This effect, can be observed at very low doses, thus suggesting that the preferential target of nonylphenols in living organisms are mitochondria.

Interactions of trialkyllead compounds with rat liver mitochondria.

The interactions of two trialkyllead (TAL) compounds, (trimethyl)Pb-Cl and (tributyl)Pb-Cl, with mitochodria from rat liver have been studied. A stimulation of the respiratory rate induced by the trialkyllead compounds added at low doses was observed which was not dependent on the presence of chloride in the medium. In contrast with the major current view, we propose that trialkyllead compounds behave as uncouplers of the oxidative phosphorylation and not (or not only) as Cl-/OH- exchangers. In fact the present results suggest that the TAL compounds enter the mitochondria as (alkyl)3Pb+ cations and are extruded as electroneutral (alkyl)3 Pb-OH compounds, the overall result being the transport of a proton through the membrane as in the case of classical uncouplers. The uncoupling effect could explain the toxicity of the compounds as a result of the decrease in the energy level of the cell. Furthermore, such a mechanism, in which the uptake of TAL compounds is supposed to be driven by a negative potential, could explain their preferential toxicity for neuronal cells, which maintain a higher negative-inside potential than most other cell types.

Mitochondrial effects of L-ropivacaine, a new local anesthetic.

The effects of the local anesthetics ropivacaine and bupivacaine were investigated on isolated rat liver mitochondria. The efficiency of oxidative phosphorylation was evaluated by measuring the rates of respiration and ATP synthesis and the magnitude of the transmembrane electrical potential (deltapsi). Bupivacaine did not alter the ADP-stimulated respiration but strongly affected the resting respiration, which was more than doubled at 0.6 mM. In addition, it decreased the transmembrane electrical potential, and the ATP synthesis rate (deltapsi was less than 100 mV at 0.6 mM). Ropivacaine did not alter the ADP-stimulated respiration, and the resting respiration seemed to be substantially unaffected up to 1.2 mM; a slight increase was observed at 1.8 and 2.4 mM. The transmembrane potential was decreased by anesthetic concentrations higher than 1.2 mM and ATP synthesis was consequently affected. The findings suggest that ropivacaine is less toxic than bupivacaine, in rat liver mitochondria.

Ni++ as a competitive inhibitor of calcium transport in mitochondria.

The kinetics of Ca++ uptake in rat liver mitochondria have been studied using the potassium diffusion potential. The advantage of this approach is that in this condition, the mitochondrial respiratory rate is not the limiting step, and therefore the effects of Ni++ on the Ca++ carrier can be studied. Our results suggest that Ni++ is a competitive inhibitor of the Ca++ carrier, but it is not transported into the mitochondria.

Mitochondrial bioenergetics as affected by cationic detergents.

This paper examines the accumulation and toxicity mechanism of a cationic detergent, cetyltrimethylammonium (bromide) (CTAB), in energized rat liver mitochondria. The results suggest that: (1) the CTAB ion is accumulated in the mitochondrial matrix by a membrane potential-driven uptake mechanism; (2) accumulation may lead to a toxic effect, since it gives rise to collapse of the mitochondrial membrane potential (delta phi) which is correlated with ATP synthesis and which regulates Ca++ uptake; (3) collapse of delta phi may be due to enhanced permeability of the mitochondrial membrane to the ions (detergent effect); and (4) delta phi collapse and Ca++ and K+ release were also observed in another cationic detergent, NTAB, but not in the presence of anionic detergents.

Anticholinesterasic drugs: tacrine but not physostigmine, accumulates in acidic compartments of the cells.

Tacrine (THA) and physostigmine (PHS) have been used in Alzheimer's disease therapy for their anticholinesterasic activity. Here we show that THA is taken up in rat lysosomes in an energy-dependent manner, and that it is also accumulated in acidic compartments of rat thymocytes and neuroblastoma cells. A concentration of THA less than 1 mM dissipated the pH gradient (delta pH) in all the above mentioned in vitro systems. On the contrary higher concentrations of PHS (1-2 mM) were ineffective. The accumulation of THA in acidic organelles of the cell may be relevant for the pharmacological action of THA in Alzheimer's treatment.

A new in vitro toxicity test based on the response to toxic substances in solutions of mitochondria from beef heart.

A simple, rapid and inexpensive in vitro method which may be used as a biological sensor for the valuation of toxicity of chemical compounds in water is proposed. The method utilizes the response of the respiratory chain of beef heart mitochondria to a wide range of toxic substances. By means of simple voltametric measurements, the method not only gives an indication of toxicity in water but, by using different substrates of the respiratory chain and exploiting some features of the toxic substances, it also allows selective detection of some toxic substance or groups of substances. Since the method reproduces the standard "rainbow trout" test, it may also be proposed as a screening test to precede whole bioorganisms bioassays or as a method to assess the presence of certain toxic substances in water.