ABSTRACT
While the dispersion of nanomaterials is known to be effective in enhancing the thermal conductivity and specific heat capacity of fluids, the mechanisms behind this enhancement remain to be elucidated. Herein, we report on highly stable, surfactant-free graphene nanofluids, based on N,N-dimethylacetamide (DMAc) and N,N-dimethylformamide (DMF), with enhanced thermal properties. An increase of up to 48% in thermal conductivity and 18% in specific heat capacity was measured. The blue shift of several Raman bands with increasing graphene concentration in DMF indicates that there is a modification in the vibrational energy of the bonds associated with these modes, affecting all the molecules in the liquid. This result indicates that graphene has the ability to affect solvent molecules at long-range, in terms of vibrational energy. Density functional theory and molecular dynamics simulations were used to gather data on the interaction between graphene and solvent, and to investigate a possible order induced by graphene on the solvent. The simulations showed a parallel orientation of DMF towards graphene, favoring π-π stacking. Furthermore, a local order of DMF molecules around graphene was observed suggesting that both this special kind of interaction and the induced local order may contribute to the enhancement of the fluid's thermal properties.
ABSTRACT
We report the effects of aqueous extracts of six marine microalgae on responses to various contractile agents in isolated rat duodenum (acetylcholine, calcium chloride, barium chloride) and vas deferens (noradrenaline). Our results suggest that only extracts of Phaeodactylum tricornutum, Skeletonema costatum, and Chlorella stigmatophora may have pharmacological potential. Extracts of these three species had spasmolytic effects on responses to the three contractile agents in duodenum. In vas deferens, P. tricornutum and C. stigmatophora inhibited the contractions induced by noradrenaline, whilst S. costatum showed a non-dose-dependent potentiation. With the aim of elucidating their mechanisms of action, we are attempting to isolate the active principles present in these extracts.
Subject(s)
Duodenum/drug effects , Eukaryota/chemistry , Muscle, Smooth/drug effects , Vas Deferens/drug effects , Animals , Female , In Vitro Techniques , Male , Muscle Contraction/drug effects , Rats , Rats, Wistar , SeawaterABSTRACT
In the course of our continuing pharmacological studies of marine microalgae, we look now at Tetraselmis suecica Stewart (Prasinophyceae) and Isochrysis galbana Demart (Haptophyceae), assessing the effects which aqueous extracts of these algae exert upon the central nervous system. To this end, we have tested for effects upon the following: spontaneous motor activity, body temperature, motor coordination, dextroamphetamine-induced hypermotility, exploratory conduct, muscle relaxation, catalepsy, conditioned avoidance response, oxotremorine-induced cholinergic syndrome, and pentylenetetrazole-induced convulsions. Our results show that aqueous extracts of both microalgae display action profiles which prove difficult to categorize by standard pharmacological criteria.
Subject(s)
Central Nervous System/drug effects , Chlorophyta/chemistry , Eukaryota/chemistry , Plant Extracts/pharmacology , Animals , Female , Male , Mice , Plant Extracts/toxicityABSTRACT
At the level of the central nervous system an aqueous extract of the marine microalga Chlorella stigmatophora (Butcher) (Chlorophyceae) showed anti-dopaminergic-type activity in assays of its effects on spontaneous motor response, rectal temperature, motor coordination, amphetamine-induced hypermotility, exploratory conduct, muscle relaxation, catalepsy, conditioned avoidance responses, oxotremorine-induced cholinergic syndrome, and pentylenetetrazole-induced convulsions.
Subject(s)
Central Nervous System/drug effects , Chlorella/chemistry , Plant Extracts/pharmacology , Animals , Female , Male , MiceABSTRACT
We report the effects of aqueous extracts of the microalga Skeletonema costatum Greve (Cleve) (Bacillariophyceae) on spontaneous motor activity, rectal temperature, motor coordination, amphetamine-induced hypermotility, exploratory behaviour, muscle relaxation, catalepsy, conditioned avoidance responses, oxotremorin-induced cholinergic syndrome, and pentylenetetrazole-induced convulsions. The S. costatum extract at dosages of 310 and 620 mg/kg works like an antidopaminergic drug with anticholinergic properties, that does not induce catalepsy and with a notable muscle relaxing activity.
Subject(s)
Central Nervous System/drug effects , Diatoms/chemistry , Animals , Female , Male , MiceABSTRACT
Continuing work on the effects of aqueous extracts of the microalgae Phaeodactylum tricornutum Bohlin (Bacillariophyceae) and Dunaliella tertiolecta Butcher (Chlorophyceae) on the central nervous system, we report their effects on spontaneous motor activity, rectal temperature, exploratory behaviour, muscle relaxation, catalepsy, and conditioned avoidance responses. Both extracts showed activity as a CNS depressant and a potential muscle relaxant, the latter more marked in the case of P. tricornutum.
Subject(s)
Central Nervous System/drug effects , Diatoms/chemistry , Animals , Male , Mice , Rats , Rats, Sprague-DawleyABSTRACT
We report the effects of aqueous extracts of the microalgae Dunaliella tertiolecta Butcher (Chlorophyceae) and Phaeodactylum tricornutum Bohlin (Bacillariophyceae) on oxotremorin-induced cholinergic symptoms, amphetamine-induced hypermotility, pentylenetetrazole-induced convulsions, and Rota-rod test performance. Both extracts significantly reduced rectal temperature, spontaneous motor activity, and time on the Rota-rod and increased the number of mice falling off the rod before 180 s, but neither protected against pentylenetetrazole-induced convulsions or against oxotremorin-induced tremor, salivation, and diarrhoea.
