Analysis of a microfluidic device for diffusion coefficient determination of high molecular weight solutes detectable in the visible spectrum.

We developed a procedure to measure diffusion coefficients using microfluidic devices that contributes to the transport analysis of high molecular weight solutes with low diffusion coefficient. This procedure allows a quick determination of diffusion coefficients and a precise evaluation of measurement errors. Making use of color variation of a pH indicator, we determined its diffusion coefficient in its own solvent (water). The value obtained was compared with previously published ones and was found to be similar to those cited. The microfluidic device has a serpentine-shaped channel that allows monitoring the solution evolution in different regions of the path in a single visual field without the need to move the camera or the microchip. This kind of device also allows the spatial and temporal tracking of the diffusion process. The solution color intensity is used to determine solute concentration; therefore, this method presents an advantage compared to those based on fluorescence detection. A complete analysis of the diffusive behavior along the channel path was performed in order to test the accuracy of these kinds of methodologies. This analysis can be used with similar devices, and the techniques employed for diffusion analysis can be applied to a µTAS-type microfluidic platform, allowing obtain variations of the diffusion coefficient as a function of time due to variations in external factors, e.g., temperature, etc.

Lateral movements in Rayleigh-Taylor instabilities due to frontiers. Experimental study.

Lateral movements of the fingers in Rayleigh-Taylor hydrodynamic instabilities at the interface between two fluids are studied. We show that transverse movements appear when a physical boundary is present; these phenomena have not been explained until now. The boundary prevents one of the fluids from crossing it. Such frontiers can be buoyancy driven as, for example, the frontier to the passage of a less dense solution through a denser solution or when different aggregation states coexist (liquid and gaseous phases). An experimental study of the lateral movement velocity of the fingers was performed for different Rayleigh numbers (Ra), and when oscillations were detected, their amplitudes were studied. Liquid-liquid (L-L) and gas-liquid (G-L) systems were analysed. Aqueous HCl and Bromocresol Green (sodium salt, NaBCG) solutions were used in L-L experiments, and CO2 (gas) and aqueous NaOH, NaHCO3, and CaCl2 solutions were employed for the G-L studies. We observed that the lateral movement of the fingers and finger collapses near the interface are more notorious when Ra increases. The consequences of this, for each experience, are a decrease in the number of fingers and an increase in the velocity of the lateral finger movement close to the interface as time evolves. We found that the amplitude of the oscillations did not vary significantly within the considered Ra range. These results have an important implication when determining the wave number of instabilities in an evolving system. The wave number could be strongly diminished if there is a boundary.

Lateral movements in Rayleigh-Taylor instabilities due to frontiers. Numerical analysis.

Numerical simulations were performed for Rayleigh-Taylor (RT) hydrodynamic instabilities when a frontier is present. The frontier formed by the interface between two fluids prevents the free movement of the fingers created by the instability. As a consequence, transversal movements at the rear of the fingers are observed in this area. These movements produce collapse of the fingers (two or more fingers join in one finger) or oscillations in the case that there is no collapse. The transversal velocity of the fingers, the amplitude of the oscillations, and the wave number of the RT instabilities as a function of the Rayleigh number (Ra) were studied near the frontier. We verified numerically that in classical RT instabilities, without a frontier, these lateral movements do not occur; only with a physical frontier, the transversal displacements of the fingers appear. The transverse displacement velocity and the initial wave number increase with Ra. This leads to the collapse of the fingers, diminishing the wave number of the instabilities at the interface. Instead, no significant changes in the amplitude of the oscillations are observed modifying Ra. The numerical results are independent of the type or origin of the frontier (gas-liquid, liquid-liquid, or solid-liquid). The numerical results are in good agreement with the experimental results reported by Binda et al. [Chaos 28, 013107 (2018)]. Based on these results, it was possible to determine the cause of the transverse displacements, which had not been explained until now.

Experimental analysis of density fingering instability modified by precipitation.

We analyze the effect of precipitate formation on the development of density induced hydrodynamic instabilities. In this case, the precipitate is BaCO3, obtained by reaction of CO2 with aqueous BaCl2. CO2(g) dissolution increases the local density of the aqueous phase, triggering Rayleigh-Taylor instabilities and BaCO3 formation. It was observed that at first the precipitate was formed at the finger front. As the particles became bigger, they began to fall down from the front. These particles were used as tracers using PIV technique to visualize the particle streamlines and to obtain the velocity of that movement. This falling produced a downward flow that might increase the mixing zone. Contrary to expectations, it was observed that the finger length decreased, indicating that for the mixing zone development, the consumption of CO2 to form the precipitate is more important than the downward flow. The mixing zone length was recovered by increasing the availability of the reactant (higher CO2 partial pressure), compensating the CO2 used for BaCO3 formation. Mixing zone development rates reached constant values at shorter times when the precipitate is absent than when it is present. An analysis of the nonlinear regime with and without the precipitate is performed.

Correlation among lesion level, muscle strength and hand function in cervical spinal cord injury.

BACKGROUND: Few epidemiological data are available regarding distribution of cervical spinal cord injury with respect to level of lesion and the relationship between the neurological level of lesion and residual hand function. Such data are important to evaluate the relevance of innovative therapeutic approaches, and to plan prospective clinical trials. AIM: To examine the frequency distribution of neurological level of lesion and to investigate the correlation among level, active muscles in the arm and the relation to hand function. DESIGN: Cross-sectional study. SETTING: Two spinal units in the Lombardy region of Italy. POPULATION: Patients with cervical spinal cord lesion. METHODS: Consecutive records, taken from an 8-year interval of admission to either spinal unit, of patients with a cervical spinal cord lesion were examined, and individuals with a C5 to C7 neurological level of lesion were called in for clinical examination. The arm muscles were evaluated according to the International Classification for Surgery of the Hand in Tetraplegia (ICSHT), and hand function was tested with the Action Research Arm Test (ARAT). A correlation analysis was made of the ICSHT, ARAT and neurological level of lesion. RESULTS: In 253 clinical records we found the most frequent lesions to be C5 (21%), C6 (31%) and C7 (21%); 76 of these patients were enrolled for a clinical evaluation. Both ICSHT (Spearmans' rho=0.6; P<0.001) and ARAT (rho=0.2; P<0.05) were poorly correlated with the neurological level of lesion. ARAT was also poorly correlated with the ICSHT group (rho=0.5; P<0.001). CONCLUSION: Our study suggests that 73% of tetraplegic subjects have a neurological level of lesion between C5 and C7, and that it is not possible to accurately predict residual hand function from the level of lesion obtained from the clinical records, or from an ICSHT evaluation. CLINICAL REHABILITATION IMPACT: The results of our work show that a large number of patients with cervical spinal cord lesion have impaired hand function. Residual hand function must be assessed with specific functional tests; it cannot be derived simply from a lesion's neurological level.

Anti-diarrhoeal and ulcer-protective effects of the aqueous root extract of Guiera senegalensis in rodents.

The anti-diarrhoeal and ulcer-protective properties of the aqueous root extract of Guiera senegalensis, a popular herbal traditional medicine in Nigeria were investigated in rats and mice. Acute toxicity studies were also carried out. The intestinal transit in mice was significantly (P < 0.05) reduced and gastric emptying delayed. One hundred and Two hundred milligrams per kilogram (p.o.) of the extract elicited a greater anti-motility activity than 0.1 mg/kg of atropine. The extract exhibited ulcer-protective properties against ethanol-induced ulceration in rats with maximal anti-ulcer activity recorded at 100 mg/kg. Guiera senegalensis also exerted significant anti-enteropooling effects causing a dose-related inhibitory effect on castor oil-induced enteropooling in rats. A profound anti-diarrhoeal activity was observed when Guiera senegalensis was tested in diarrhoeic mice. The frequency of defaecation as well as the wetness of the faecal droppings was significantly reduced. Furthermore, the extract produced 100% inhibition of castor oil-induced diarrhoea in mice. The oral LD50 values obtained were > 5000 mg/kg in both mice and rats. The results support the folkloric applications of Guiera senegalensis for the treatment of diarrhoea and ulcer in Nigerian herbal traditional medicine.

Neuropharmacological effects of the aqueous extract of Nauclea latifolia root bark in rats and mice.

The present study evaluated the neuropharmacological effects of the aqueous extract of Nauclea latifolia root bark in rodents. Effects on the spontaneous motor activity (SMA), exploratory behaviour, pentobarbital sleeping time, apomorphine-induced stereotypic behaviour and motor coordination (rota-rod performance) were investigated. The extract (50-200 mg/kg p.o.) significantly (P<0.05) decreased the SMA and exploratory behaviour in mice and prolonged pentobarbital sleeping time in rats dose-dependently. The extract also remarkably attenuated the intensity of apomorphine-induced stereotypy dose-dependently in mice, but had no effect on motor coordination as determined by the performance on rota-rod. These results indicate the presence of psychoactive substances in the aqueous extract of the root bark of Nauclea latifolia.

Effect of aqueous leaf extract of Irvingia gabonensis on gastrointestinal tract in rodents.

Effect of the aqueous leaf extract of I. gabonensis on the gastrointestinal tract was investigated on isolated rabbit jejunum, guinea pig ileum, gastrointestinal motility, castor oil-induced diarrhoea in mice and castor oil-induced fluid accumulation in rats. The results showed that the extract exhibited a concentration-dependent relaxation of spontaneous pendular movement of isolated rabbit jejunum and guinea pig ileum, and attenuated both acetylcholine-induced contraction of rabbit jejunum and histamine-induced contraction of guinea pig ileum. The extract (100, 200 and 400 mg/kg) also caused a significant dose-dependent decrease of gastrointestinal motility in mice (40.12, 39.45 and 37.45%), intestinal fluid accumulation in rats (71.43, 81.63 and 83.27%), and remarkably protected mice against castor oil-induced diarrhoea [58.33, 75 and 91.67% (Di Carlo score)] respectively. Preliminary phytochemical screening of the aqueous leaf extract of I. gabonensis revealed the presence of saponins, tannins, phenols and phlobatanins.

Postsynaptic dopamine (D(2))-mediated behavioural effects of high acute doses of artemisinin in rodents.

Artemisinin or qinghaosu is the active principle of quinghao (Artemisia annua L.) developed from Chinese traditional medicine, which is now widely used around the world against falciparum malaria. Behavioural effects of high acute doses of artemisinin were studied on spontaneous motor activity (SMA), exploratory behavior, apomorphine-induced stereotype behavior and pentobarbital sleeping time in mice and rats in order to provide additional evidence on its safety profile on the central nervous system (CNS). Effects of the drug on bromocriptine-induced hyperactivity in short term reserpinised mice were also evaluated. Intraperitoneal (i.p.) injection of artemisinin at doses of 50 and 100mg/kg, significantly (P<0.05) reduced the SMA in mice, prolonged the pentobarbital sleeping time in rats, and attenuated the apomorphine-induced stereotypy in mice. Mice pretreated with reserpine, showed a significant decrease in locomotor activity compared to the saline-treated group. Bromocriptine, a D(2) receptor agonist, induced locomotor activity in mice pretreated with reserpine which was attenuated by artemisinin. The results suggest that artemisinin possesses sedative property, which may be mediated via postsynaptic dopamine (D(2)) receptor in the CNS.

Smooth muscle contraction induced by Indigofera dendroides leaf extracts may involve calcium mobilization via potential sensitive channels.

The contractile effects of the aqueous extract of the leaves of Indigofera dendroides (ID) were studied on the gastrointestinal motility in mice and isolated smooth muscle preparations obtained from rats and guinea pigs. The contractile effects of 10(-6) M acetylcholine, 80 mM KCl and 1.6 mg/ml ID were measured on the rat ileal smooth muscle exposed to calcium-free buffer or physiological solution, to determine the calcium pools mobilized by extract for activation of contraction. Acute toxicity test (LD(50)) was also carried out in mice. The result showed that ID (0.05-3.2 mg/ml) produced a concentration-dependent contraction of the guinea pig and rat ileum. These responses were not blocked by mepyramine (2.49 x 10(-9) M), verapamil (8.14 x 10(-9) M), or pirenzepine (4.7 x 10(-7) M), but were blocked completely by atropine (2.92 x 10(-9) M). A significant increase in propulsion of gastrointestinal motility was observed. Acetylcholine, KCl and ID produced contractions in Ca(2+) free media. The phasic components of the contractile responses to Ach as well as the tonic component of K(+) and ID-induced contractions were relatively resistant to short periods of calcium-free exposure. Ach, K(+) and ID still caused contractions in the presence of verapamil. The data revealed that ID-induced contractions were not mediated by histaminergic receptors, calcium channels, M1 muscarinic receptors. It also suggests that Ach mobilize Ca from some tightly bound or intracellular pool, whereas high K(+) and ID may mobilize Ca from some superficial or loosely-bound pool.

Effect of the aqueous extract of Chrysanthellum indicum on calcium mobilization and activation of rat portal vein.

The effects of the aqueous extract of Chrysanthellum indicum (CI) on calcium activation and mobilization were studied using the rat portal vein. The extract caused a concentration-dependent contraction of the portal vein. KCl (80 mM), norepinephrine (NA, 10(-6)M) and CI (4 mg/ml) evoked sustained contraction of the portal vein. In Ca-free medium (with EGTA) the contractions evoked by these agents were reduced significantly. The times-to-peak of KCl, NA and CI were similar -in normal PSS, but in Ca-free medium the times-to-peak for KCl and CI were greatly increased. The contractions induced by CI were not inhibited by chlorpropamide and prazosin, but were blocked by verapamil. The data obtained suggest that the aqueous extract of CI utilizes extracellular calcium pools to bring about contractile response and this effect might be mediated through the activation of potential-sensitive channels.

Central inhibitory activity of the aqueous extract of Crinum giganteum.

The aqueous extract of Crinum giganteum given intraperitoneally at doses of 6.25, 12.5 and 25 mg/kg in rats prolonged the duration of pentobarbital sleeping time and in mice reduced spontaneous motor activity, decreased the exploratory activity and attenuated amphetamine-induced stereotype behavior. The intraperitoneal and oral preliminary LD(50) in mice were found to be 627 and 1468 mg/kg, respectively. The data obtained suggest that the aqueous extract of C. giganteum contains some biologically active principles with sedative activity.

Effect of the aqueous extract of African mistletoe, Tapinanthus sessilifolius (P. Beauv) van Tiegh leaf on gastrointestinal muscle activity.

Effects of the aqueous extract of T. sessilifolius on the gastrointestinal muscle were investigated on smooth muscle preparations isolated from rabbit jejunum, guinea pig ileum and on gastrointestinal transit in mice. Elemental analysis of the extract was also carried out. The aqueous extract of T. sessilifolius evoked a concentration dependent contraction of the rabbit jejunum and guinea pig ileum. The contractions evoked by the extract were not attenuated either by atropine or mepyramine, but they were completely blocked by verapamil. The elemental analysis revealed the presence of Mg, Zn, Fe, Cu, and very high concentration of Ca. The intraperitoneal LD50 in mice was found to be 1500 mg/kg. The aqueous extract of T. sessilifoliius possesses active components that may be mediating the observed biological activity through calcium mobilization.

Sedative effects of the methanolic leaf extract of Newbouldia laevis in mice and rats.

The effect of the methanolic extract of Newbouldia laevis seem on the central nervous system of rats and mice was investigated. The extract was tested on spontaneous motor activity, exploratory behaviour, apomorphine induced climbing behaviour in mice and pentobarbital induced hypnosis in rats. The extract caused considerable reductions of exploratory activity, spontaneous motor activity and prolonged pentobarbitone-induced hypnosis in rats. It was also found to attenuate apomorphine climbing in mice. The results suggest that the methanolic extract of Newbouldia laevis may contain principles that have sedative properties.

Neuropharmacological effect of the aqueous extract of Sphaeranthus senegalensis in mice.

Effects of the aqueous extract of Sphaeranthus senegalensis Vaill. (Family: Compositae) were studied on spontaneous motor activity, exploratory behaviour, rota-rod performance and pentobarbital sleeping time in mice. Preliminary phytochemical evaluation and acute toxicity (LD(50)) values were also studied. The extract (50 and 100 mg/kg p.o.) produced reduction in spontaneous motor activity, exploratory behaviour and motor coordination and prolonged pentobarbital sleeping time. Glycosides, saponins and tannins were shown to be present in the extract. The i.p. LD(50) in mice was 2735.61 and 5000 mg/kg orally. The results suggest that the aqueous extract of S. senegalensis contains some active principles, which may be sedative in nature.

Evaluation of methanolic extract of Ficus platyphylla on gastrointestinal activity.

Methanolic extract of Ficus platyphylla was tested on isolated rabbit jejunum, rat duodenum and gastrointestinal motility in mice. The extract showed a biphasic effect on isolated smooth muscle. Lower concentration of extract caused contraction, while higher concentrations produced relaxation. The contractile phase was attenuated by atropine, while relaxant phase attenuated histamine induced contraction of guinea pig ileum. The extract also exhibited a dose-dependent inhibition of gastrointestinal motility. Acute toxicity test in mice established LD50 value (i.p.) of the extract to be 2000 mg/kg. Preliminary phytochemical screening of the extract gave positive test for flavonoids, tannins and saponins.

Spasmolytic activity of methyl angolensate: a triterpenoid isolated from Entandrophragma angolense.

Entandrophragma angolense is a medicinal plant used in folk medicine against several diseases including peptic ulcer. Methyl angolensate was isolated from E. angolense by recrystallization from methanol. The needle-like crystals were characterized and tested on isolated rabbit jejunum, guinea pig ileum and the rat fundus strip. The compound was also evaluated on the gastrointestinal transit in mice. The results showed that the compound exerted significant concentration dependent inhibition of smooth muscle and reduced the propulsive action of the gastrointestinal tract in mice. The relaxation observed did not attenuate acetylcholine and histamine induced contractions, but was found to inhibit contractions induced by serotonin. It is therefore suggested that methyl angolensate may exert its activity on gastrointestinal smooth muscle via serotonergic mechanisms.

Pharmacological effects of the aqueous extract of Neorautanenia mitis in rodents.

The pharmacological effects of the aqueous extract of Neorautanenia mitis (family Papilonaceae) were studied in rodents. Investigations were carried out on acetic acid-induced writhing (pain) in mice and hind paw oedema in rats. The effects of the extract were also studied on the isolated non-pregnant rat uterus and rabbit jejunum. Results showed the extract to possess significant (P<0.05) dose-dependent anti-nociceptive activity between 12.5 and 50.0 mg/kg p.o. in mice and slight anti-inflammatory activity at 25 and 50 mg/kg p.o. in rats. The extract also produced a concentration-dependent inhibition of the normal rhythmic contraction of the isolated non-pregnant rat uterus. It was found to inhibit oxytocin-induced as well as acetylcholine-induced contractions in the rat uterus. The extract also exhibited concentration-dependent inhibition of spontaneous contractions of the rabbit jejunum. Preliminary phytochemical analysis of the extract revealed the presence of saponin glycosides, flavonoids, tannins and alkaloids. The extract had an intraperitoneal (i.p.) LD(50) of 282.84+/-3.2 mg/kg in mice. These data corroborate the traditional use of this plant in the treatment of dysmenorrhea.

Antidiarrhoeal and antiulcerogenic effects of methanolic extract of Asparagus pubescens root in rats.

The effect of methanolic extract of Asparagus pubescens root on experimentally-induced diarrhoea and ulceration was investigated in rats. The extract (500-1500 mg/kg) dose-dependently, reduced significantly the intestinal propulsive movement, castor oil-induced diarrhoea and intestinal fluid accumulation. Yohimbine an alpha(2)-adrenoceptor blocker attenuated the antidiarrhoeal effect of the extract. The extract also reduced the ulcer indices induced by indomethacin and ethanol in a dose-related manner. The results indicate that its antidiarrhoeal and antiulcerogenic effects might in part be due to its alpha(2)-adrenoceptor stimulation and its active constituents respectively.