Evaluation of trace elements in selected foods and dietary intake by young children in Thailand.

Elemental concentrations in rice, animal products, eggs, vegetables, fruits, infant formulas and drinking water were determined in 667 food samples randomly collected from local markets, big supermarkets and grocery stores in Bangkok, Thailand, during the period October 2005-August 2008. Samples were digested with nitric acid and analysed by inductively coupled plasma-mass spectrometry. Arsenic and cadmium levels in most foods were below the maximum levels as set by international organisations. Filtered and bottled drinking water, rice, vegetables and banana contained low concentrations of arsenic, cadmium and lead. Non-polished rice had higher magnesium, calcium, manganese, iron and selenium concentrations than polished rice. Banana was a major source for manganese and selenium. Pig kidney and liver contained high levels of arsenic and cadmium. Manganese, cadmium, lead and aluminium concentrations in soybean milk could also be of concern. With respect to food safety for children, the amounts of arsenic and cadmium ingested with poultry, pig liver or rice corresponded to high weekly or monthly intake.

Fractional analysis of arsenic in subsurface-flow constructed wetlands with different length to depth ratios.

Arsenic (As) removal in subsurface-flow constructed wetlands (CW) planting with vetiver grasses was experimented by comparing between two different configurations; (i) deep-bed units (dpCW) with length to depth (L:D) ratio=2 and (ii) shallow-bed units (shCW) with L:D ratio=8; operating at hydraulic retention time (HRT) of 6, 9, and 12 days. The tracer study of CW units revealed that no effect of L:D ratio on dispersion number could be determined, but affecting to the effective volume ratio. Based on the data obtained from the pilot-scale experiments of CW units for 117 days, it is apparent that the dpCW could achieve relatively high As removals (52.9%, 59.2%, and 72.1% at HRT of 6, 9, and 12 days, respectively). Analysis of As mass balance showed that only 0.2-0.4% of As input was uptaken by vetiver grasses whereas the major portion was retained in the CW media (38.9-77.6%). Forms of the retained As was determined by sequential fractionation which could indicate As complexation with iron and manganese on the media surface of 31-38% and As trapping into the media of 42-52% of the total. No obvious difference of As fractions in bed of between dpCW and shCW units was observable.

PROGRAMMABLE DIELECTROPHORETIC µTAS SAMPLE HANDLING.

We present the concept of a general-purpose sample analysis platform (GSAP) based on dielectrophoretic methods. The platform architecture comprises integrated functional blocks that can be programmed to perform a diverse range of analysis steps, including the on-device preparation of real world samples.

Arsenic removal efficiency and mechanisms by electro-chemical precipitation process.

This research was conducted to investigate the efficiency and mechanisms of arsenic (As) removal from a contaminated water by using the electro-chemical precipitation (ECP) process, with the operating conditions as follows: initial As concentration of 0.5-5 mg/L, 0.1 M KCl, electrical gradient of 200 V/m and initial pH higher than 3. The laboratory-scale ECP unit was able to reduce As to within the WHO drinking water standard of 0.01 mg/L in 20 min. The Cl- salt was found to yield better As removal efficiencies than the NO3- salt probably because NO3- ions interfered with the production of OH- and Fe(OH)3, important for As removal. X-ray fluorescence and X-ray diffractometric analysis revealed maghemite (Fe2O3) and angelellite (Fe4As2O11) to be the major compounds present in the precipitated sludge. The percent Fe2O3 and Fe4As2O11 contents of the dried ECP sludge were 98.29% and 0.26%, respectively. From a mass balance analysis, As removal in the ECP process was due to: incorporation in and adsorption on the ECP sludge--64.9-94.9%, conversion to arsine (AsH3) gas--10.5-15.6%, adsorption on the electrode plates and reactor walls--0.03-1.1%, residual in the supernatant--0.2-0.4%, and unaccounted for--1.2-19.8%.

Effect of chronic K+ deficiency on contractile properties of soleus muscle in rats: evidence of sex differences.

1. Alterations in skeletal muscle function of chronically K(+)-depleted male and female rats were investigated in isolated soleus muscles. 2. By 16 weeks K+ deficiency, plasma K+ concentrations in both male and female rats were reduced to approximately 2 mEq/L, which was accompanied by an approximate 50% reduction in muscle K+ content and a marked increase in muscle Na+ content. These changes were similar in both males and females. 3. Plasma creatine phosphokinase activity progressively increased with time in K(+)-depleted male rats, whereas only a slight increase was observed in female rats. 4. Maximum isometric twitch tension (Pt) and tetanic tension (Po) of K(+)-depleted soleus muscles from male rats was markedly suppressed; this was not seen for soleus muscles obtained from female rats. 5. After exposure to insulin in low-K+ solution, the contractile tension of soleus from the K(+)-depleted male rats was suppressed to a greater extent. 6. All alterations in muscle function during chronic K+ depletion were restored to normal after 2 weeks K+ repletion. 7. The results suggest that there is a preponderance for male over female rats in developing alterations in skeletal muscle function during chronic K+ deficiency. The changes may be associated with abnormalities of muscle membrane permeability and cellular function.

Dielectrophoretic detection of changes in erythrocyte membranes following malarial infection.

The dielectric properties of normal erythrocytes were compared to those of cells infected with the malarial parasite Plasmodium falciparum. Normal cells provided stable electrorotation spectra which, when analyzed by a single-shelled oblate spheroid dielectric model, gave a specific capacitance value of 12 +/- 1.2 mF/m2 for the plasma membrane, a cytoplasmic permittivity of 57 +/- 5.4 and a cytoplasmic conductivity of 0.52 +/- 0.05 S/m. By contrast, parasitized cells exhibited electrorotation spectra with a time-dependency that suggested significant net ion outflux via the plasma membrane and it was not possible to derive reliable cell parameter values in this case. To overcome this problem, cell membrane dielectric properties were instead determined from dielectrophoretic crossover frequency measurements made as a function of the cell suspending medium conductivity. The crossover frequency for normal cells depended linearly on the suspension conductivity above 20 mS/m and analysis according to the single-shelled oblate spheroid dielectric model yielded values of 11.8 mF/m2 and 271 S/m2, respectively, for the specific capacitance and conductance of the plasma membrane. Unexpectedly, the crossover frequency characteristics of parasitized cells at high suspending medium conductivities were non-linear. This effect was analyzed in terms of possible dependencies of the cell membrane capacitance, conductance or shape on the suspension medium conductivity, and we concluded that variations in the membrane conductance were most likely responsible for the observed non-linearity. According to this model, parasitized cells had a specific membrane capacitance of 9 +/- 2 mF/m2 and a specific membrane conductance of 1130 S/m2 that increased with increasing cell suspending medium conductivity. Such conductivity changes in parasitized cells are discussed in terms of previously observed parasite-associated membrane pores. Finally, we conclude that the large differences between the dielectrophoretic crossover characteristics of normal and parasitized cells should allow straightforward sorting of these cell types by dielectrophoretic methods.

The in vivo and in vitro effects of caffeine on rat immune cells activities: B, T and NK cells.

The effect of caffeine (naturally occurring plant methylxanthine) on immunological cell activities in Sprague-Dawley rat both in vivo and in vitro was studied. A cytotoxic assay was done to study natural killer (NK) cells and a proliferation assay was performed for T and B cell activities. Three different doses of caffeine i.e., 2, 6 and 18 mg/kg/day were administered chronically to Sprague-Dawley rats to assess the effects in vivo. Both NK cell cytotoxicity and B cell proliferative response to pokeweed mitogen (PWM) showed significant decreases (P less than 0.05) in rats treated with 6 mg/kg/day, whereas the T cell proliferative response to phytohemagglutinin-P (PHA-P) was significantly increased (P less than 0.05) in the rats treated with 18 mg/kg/day. In vitro, caffeine significantly decreases (P less than 0.05) B and T cell proliferative responses to PWM and PHA-P at added caffeine concentrations of 10, 20 and 40 micrograms/ml. However, no effect was observed on NK cells activity. Furthermore, in vitro, a broader dose range of caffeine (1, 10, 100 and 1,000 micrograms/ml) exhibited dose-dependent inhibition of both B and T cell proliferative responses.

Flunarizine and verapamil inhibit chloroquine-resistant Plasmodium falciparum growth in vitro.

Using pharmacological properties in relation to the biochemistry of P. falciparum, verapamil, flunarizine, and chlorpromazine which are calcium blockers were selected to test for their antimalarial activity against P. falciparum in vitro. Results revealed that the drugs inhibited parasite population growth in the following order of IC50: verapamil 1 X 10(-6) M, chlorpromazine 3.5 X 10(-6) M, and flunarizine 5 X 10(-6) M. These three calcium blockers have antimalarial effects on chloroquine resistant parasite (alone T9/94) but are less potent when compared with the efficacy of quinine or mefloquine in vitro.

Alteration of medullary respiratory unit discharge by iontophoretic application of putative neurotransmitters.

1 Cats with midcollicular decerebration were vagotomized, paralyzed and artificially ventilated. Phrenic nerve activity was recorded as an index of central respiratory rhythm. Medullary respiratory neurones and non-respiratory cells located in approximation to the ventral respiratory nucleus were tested for their responsiveness to iontophoretically applied gamma-aminobutyric acid (GABA), acetylcholine (ACh) and glutamate. 2 GABA tended to inhibit, whereas ACh and glutamate excited activity both of respiratory and non-respiratory units. Some phase-spanning respiratory unit activities were converted to phasic discharge patterns linked to either inspiration or expiration concomitant with application of low GABA doses. Appropriate applications of GABA also resulted in a complete cessation of the respiratory or non-respiratory neuronal activities. 3 While application of ACh or glutamate induced continuous firing in phasic, phase-spanning respiratory neurones, the periodic discharge patterns of inspiratory or expiratory units was not altered by ACh or, in many instances, by glutamate. Only at high doses of glutamate was the phasic discharge of some inspiratory or expiratory units converted to tonic activity. 4 These observations suggest that strong inhibitory processes serve to maintain the phasic firing pattern of respiratory units. These data also support the concept that active-inhibitory phase-switching mechanisms serve to define respiratory rhythmicity.

Iontophoretic studies of histamine and histamine antagonists in the feline vestibular nuclei.

The activity of single neurons in the vestibular neuronal complex of midcollicular decerebrate, decerebellectomized cats were recorded and their responsiveness to iontophoretically applied histamine and other agents determined. The majority of the cells tested were inhibited by iontophoresis of histamine while 24% were excited by this agent. Neurons exhibiting inhibitory responses were widely distributed throughout the four vestibular nuclei and adjacent reticular formation whereas excitatory responses to histamine were obtained mainly in the region of the lateral vestibular nucleus. The H2-receptor blocking agents metiamide and cimetidine were examined as to their actions on spontaneously firing cells and cells affected by histamine. Metiamide was selective in blocking histamine-induced inhibition but not excitation while cimetidine was ineffective in blocking either response. These results suggest that histamine has both inhibitory and excitatory actions on brain stem neurons and metiamide is an effective antagonist of histamine-induced inhibition.

Antagonism of the effect of isoprenaline on heart rate by pilocarpine.

1 The interaction of pilocarpine and isoprenaline on heart rate was investigated in the spontaneously beating, right isolated atrium of the rat.2 The log dose-effect curve of isoprenaline, measured in the presence of various concentrations of pilocarpine, was not modified when the concentration of the latter did not exceed 10(-6)M even though significant slowing of the heart had occurred. At concentrations higher than 10(-6)M a rapid but graded shift to the right of isoprenaline response curves occurred so that at pilocarpine 10(-5)M the pD(2) of isoprenaline was reduced from 11 to 3.3; cocaine slightly reduced this antagonism.3 It is concluded that pilocarpine antagonizes isoprenaline by some mechanism which is not of the simple competitive type.

Mechanism of catecholamine antagonism in rat heart produced by pilocarpine and related drugs.

1 High concentrations of pilocarpine and methacholine consistently lowered the potencies of a series of adrenoceptor agonists as shown by displacement of complete cumulative dose-effect curves for their positive chronotropic action on rat isolated atria. The order of potency of the agonists was characteristic of beta-adrenoceptor activation and this was converted to the type which characterizes alpha-adrenoceptor activation when pilocarpine was present.2 Propranolol effectively blocked the adrenoceptor agonists in the presence of pilocarpine and phentolamine abolished the antagonistic actions of pilocarpine. Atropine, which by itself did not affect the action of the adrenoceptor agonists, abolished both the bradycardia and antagonism produced by pilocarpine.3 It is concluded that pilocarpine antagonizes adrenoceptor agonists by muscarinic cholinoceptor activation without involving classical adrenoceptors.