RESUMEN

The human immune response can be divided into two arms: innate and adaptive immunity. The innate immune system consists of "hard-wired" responses encoded by host germline genes. In contrast, the adaptive response consists of gene elements that are somatically rearranged to assemble antigen-binding molecules with specificity for individual foreign structures. In contrast to the adaptive immune system, which depends upon T and B lymphocytes, innate immune protection is a task performed by cells of both hematopoietic and non-hematopoietic origin. Hematopoietic cells involved in innate immune responses include macrophages, dendritic cells, mast cell, neutrophils, eosinophils, natural killer (NK) cells and natural killer T cells. The induction of an adaptive immune response begins when a pathogen is ingested by an Antigen Presenting Cell (APC), such as the Dendritic cell (DC), in the infected tissue. DCs bridge the gap between first line innate responses and powerful adaptive immune responses, by internalizing, processing and presenting antigens on Major Histocompatibility Complex (MHC) and MHC-like molecules to the adaptive immune cells In addition to DCs, macrophages and B cells are deemed antigen presenting cells (Llewelyn & Cohen, 2002).

Asunto(s)

RESUMEN

Every year there are > 33 million cases of Respiratory Syncytial Virus (RSV)-related respiratory infection in children under the age of five, making RSV the leading cause of lower respiratory tract infection (LRTI) in infants. RSV is a global infection, but 99% of related mortality is in low/middle-income countries. Unbelievably, 62 years after its identification, there remains no effective treatment nor vaccine for this deadly virus, leaving infants, elderly and immunocompromised patients at high risk. The success of all pathogens depends on their ability to evade and modulate the host immune response. RSV has a complex and intricate relationship with our immune systems, but a clearer understanding of these interactions is essential in the development of effective medicines. Therefore, in a bid to update and focus our research community's understanding of RSV's interaction with immune defences, this review aims to discuss how our current knowledgebase could be used to combat this global viral threat.

Asunto(s)

RESUMEN

This work reports the design and construction of a novel potentiostat which features an integrator transimpedance amplifier as a current-monitoring unit. The integration approach addresses the limitations of the feedback resistor approach used for current monitoring in conventional potentiostat designs. In the present design, measurement of the current is performed by a precision switched integrator transimpedance amplifier operated in the dual sampling mode which enables sub-pA resolution. The potentiostat is suitable for measuring very low currents (typical dynamic range: 5 pA-4.7 µA) with a 16 bit resolution, and it can support 2-, 3- and 4-electrode cell configurations. Its operation was assessed by using it as a detection module in a home-made capillary electrophoresis system for the separation and amperometric detection of paracetamol and p-aminophenol at a 3-electrode microfluidic chip. The potential and limitations of the proposed potentiostat to implement fast potential-scan voltammetric techniques were demonstrated for the case of cyclic voltammetry.

RESUMEN

The precision characteristics of the absorbance measurements obtained with a low-cost miniature spectrometer incorporating an array detector were evaluated. Uncertainties in absorbance measurements were due to a combination of non-uniform light intensity and detector response over the wavelength range examined (350-850 nm), in conjunction with the digitization of the intensity indications and the intrinsic noise of the detecting elements. The precision characteristics are presented as contour plots displaying the expected RSD% of absorbances on the absorbance versus wavelength plane. The minimum RSD% for the spectrometer configuration tested was observed within the 0.2-1.5 absorbance units and 500-750 nm wavelength range. Without invoking signal enhancement features of the data-acquisition program (scan average, higher integration times, smoothing based on averaging the signal detected by adjacent pixels), the attainable precision within this range was 0.4-0.8%. A computer program based on Monte Carlo simulations was developed for the prediction of absorbance precision characteristics under various conditions of measurements.

RESUMEN

Direct detection of ephedrines and other underivatized amino compounds (amines, alicyclic amines, alkanolamines, and amino acids) can be carried out via electrocatalytic oxidation at a carbon paste electrode (CPE) modified with cobalt phthalocyanine (CoPC) in alkaline solution (0.10 mol L-1 NaOH). Most of the amino compounds tested could be determined using the CoPC/CPE in an amperometric flow detector. The analytical signal of ephedrine was stabilised by alternating the potential between an anodic detection potential of +0.30 V (+0.45 V for other amino compounds) applied for 220 ms and a cathodic reactivation potential of -0.30 V applied for 100 ms (potentials versus SCE). The linear response range for ephedrine was within 1-100 mumol L-1 and the detection limit was 0.8 mumol L-1 with a 100 microL sample loop and a typical sampling ra 60 h-1. The signal (oxidation peak current) reproducibility was 2-3%. The method was applied to the determination of ephedrine in pharmaceutical formulations with results comparable to those obtained with a standard spectrophotometric method.

Asunto(s)

RESUMEN

A novel automated flow-injection spectrophotometric method for the determination of catecholamines (epinephrine and isoproterenol) has been developed based on the formation of their coloured complexes with Fe(II) in aminoacetic-carbonate buffer pH 8.3 and measuring of the absorbance peaks at the lambda(max) of 530 nm. A fully automated FIA system controlled by home-made software (FIA-MOD) was used for optimising the chemical and manifold parameters and running of routine measurements. The calibration graph was linear in the range of 5-200 mg l(-1) for epinephrine with an RSD of 0.24% (n = 5; c = 150 mg l(-1)) and 10-300 mg(-1) for isoproterenol with an RSD of 0.13% (n = 5; c = 200 mg l(-1)). Measurement throughput was 120 h(-1) ensuring a sample throughput of 40 h(-1) analysed in triplicate. Common excipients for tablets and injections were found not interfering. The proposed method was applied for the assay of various commercial pharmaceutical formulations containing epinephrine and isoproterenol and for the content uniformity test for the isoproterenol tablets. The assay results with RSD 2-4% (n = 3) were comparable with those obtained with the official USP XXIII methods (mean difference 1.9%).

Asunto(s)

RESUMEN

The possibility of determination of twelve flavonoids (fisetin, galangin, hesperetin, hesperidin, kaempherol, morin, myricetin, naringin, quercetin, quercitrin, rutin, rhamnetin) using adsorptive stripping voltammetry in a flow injection system is examined. Carbon paste electrodes based on mixtures of nujol-graphite and diphenylether-graphite were used and compared as working electrodes and measurements were made using both 'direct' and 'medium-exchange' procedures. The effect of experimental parameters such as pH, accumulation potential and period, presence of various compounds was examined. Sample size (typically 0.33 ml) is greatly reduced by applying a reciprocating flow of the sample plug through the detector during the preconcentration step. The instrumental sensitivities and lower detection limits were calculated for all flavonoids in all cases. In some cases the differences are so high that determination of certain flavonoids in the presence of excess of others is allowed. Depending on the flavonoid, the electrode type, and the measurement procedure the analytical range and the reproducibility (RSD%) were 10(-5)-10(-8) M and 2.5-10%, respectively. A simple procedure is developed for the electrochemical determination of rutin in a multivitamin preparation.

RESUMEN

Contemporary analytical methodology allows the determination of substances in ultra-dilute solutions, i.e. picomol per liter (pM) and lower, by employing a wide spectrum of techniques. The reduction of both sample volume and quantification limits made possible the determination of zeptomol amounts of analytes. Among the many problems associated with the analysis of this kind of sample is the relatively high intrinsic sampling variance which restricts the attainable overall analytical precision. This sampling variance is due to the quantized nature of matter. The expected sampling variance can be calculated considering that the limited number of analyte molecules per test-portion is subjected to Poisson distribution.

RESUMEN

A simple, rapid and fully automated flow injection method with fluorimetric detection after hydrolysis with H2SO4 in ethanolic or methanolic medium at room temperature has been developed for the determination of 1,4-benzodiazepines (oxazepam, diazepam and nitrazepam) in pharmaceutical formulations. The calibration curves are linear in the ranges (mg ml(-1)) of oxazepam (0.025-0.150), diazepam (0.010-0.125) and nitrazepam (0.010-0.150), with detection limits of 0.01, 0.005 and 0.005 mg ml(-1), respectively, and RSD (1% (n = 10). The measurement throughput is 60 h(-1) using a 200-microl sample volume obtained by the direct dissolution of formulations in alcohol.

Asunto(s)

RESUMEN

This paper deals with some applications of Virtual Instrumentation to electroanalytical measurements. Virtual Instruments (VIs) are software programmes that simulate the external appearance and functions of a real instrument on the screen of a computer. In this work, programmes have been developed to control the potential of a working electrode (through a suitable potentiostat), acquire the current response, process the acquired current signal, and control a peristaltic pump and injection valve. The sequence of operations was controlled by the VI. The programmes developed have been applied to amperometric and voltammetric measurements in static and flowing solutions. The Vl package that has been used was Lab VIEW 4.0.1 from National Instruments.

Asunto(s)

RESUMEN

A flow injection configuration for the spectrofluorimetric determination of magnesium is proposed. The method is based on the formation of a strongly fluorescent complex of magnesium ion with 2-hydroxy-1-naphthaldehyde salicyloylhydrazone in alkaline, aqueous-ethanolic (50% v/v) solutions. The optimal chemical conditions for complex formation in the mixed solvent were studied and the flow injection manifold was optimized and used for the determination of magnesium in 1000-fold diluted serum samples without any other pre-treatment. The measurement throughput was 120 h-1. The detection limit of the method was 2 micrograms l-1 (2 mg l-1 for serum). The concentration range of application is 4.8-120 micrograms l-1 (0.2-5.0 mumol l-1). Within-run relative standard deviations for the method at 4.8, 24 and 120 micrograms l-1 of magnesium were 3.5, 1.2 and 0.7%, respectively. Analytical recoveries range from 96.2 to 102% (mean 98.8%).

Asunto(s)

RESUMEN

The bromide released by the alkaline hydrolysis of N-bromosuccinimide and its reactions with bromide, pyridoxine and thiamine have been studied potentiometrically using a solid-state bromide-selective electrode to monitor the consumed or produced bromide ion. Potential-time indications are obtained using a microcomputer-controlled potentiometric system. The overall rate constants and the activation energies have been calculated. A kinetic-potentiometric procedure for the determination of pyridoxine in the presence of thiamine in pharmaceutical preparations, based on its reaction with N-bromosuccinimide, is presented.

RESUMEN

A method is proposed for the determination of 0.0500-1.00 microgram ml-1 of epinephrine and L-dopa and 0.100-1.00 micrograms ml-1 of norepinephrine and dopamine by their chemiluminogenic oxidation with potassium permanganate in acidic medium, in the presence of formaldehyde, which greatly improves the sensitivity. Flow injection allows the measurement of 80 solutions per hour. The method was also optimized for a continuous-flow system. Comparative results from numerous organic compounds proved the necessity for electron-donating groups on the benzene ring for sensitive chemiluminescent characteristics.

Asunto(s)

RESUMEN

The effect of various surfactants [the cationics cetyl trimethyl ammonium bromide (CTAB) and cetyl pyridinium chloride (CPC), the anionic sodium dodecyl sulphate (SDS), and the nonionic polysorbate 80 (Tween 80)] on the solubility and ionization constant of some sparingly soluble weak acids of pharmaceutical interest was studied. Benzoic acid (and its 3-methyl-, 3-nitro-, and 4-tert-butyl-derivatives), acetylsalicylic acid, naproxen and iopanoic acid were chosen as model examples. Precise and accurate acid-base titrations in micellar systems were made feasible using a microcomputer-controlled titrator. The response curve, response time and potential drift of the glass electrode in the micellar systems were examined. The cationics CTAB and CPC were found to increase considerably the ionization constant of the weak acids (delta pKa ranged from -0.21 to -3.57), while the anionic SDS showed negligible effect and the nonionic Tween 80 generally decreased the ionization constants. The solubility of the acids in aqueous micellar and acidified micellar solutions was studied spectrophotometrically and it was found increased in all cases. Acetylsalicylic acid, naproxen, benzoic acid and iopanoic acid could be easily determined in raw material and some of them in pharmaceutical preparations by direct titration in CTAB-micellar system instead of using the traditional non-aqueous or back titrimetry. Precisions of 0.3-4.3% RSD and good correlation with the official tedious methods were obtained. The interference study of some excipients showed that a preliminary test should be carried out before the assay of formulations.

Asunto(s)

RESUMEN

The use of isoflurane in patients with coronary artery disease remains controversial because of the possibility of "coronary steal". In this study, the effects of isoflurane and halothane on global and regional myocardial blood flow and metabolism were compared, and the relationship between steal-induced myocardial ischemia and the administered volatile anesthetic was investigated in 40 patients with steal-prone coronary anatomy undergoing elective coronary artery bypass operations. The patients were randomly assigned to receive either isoflurane or halothane (0.5 MAC inspired concentration) immediately after induction with fentanyl (50 micrograms/kg). Hemodynamic measurements and blood samples were obtained at preinduction, postintubation, preincision, poststernotomy, at 60 min after beginning isoflurane or halothane, and precannulation (a total of 238 study events). Throughout the study, heart rate was kept constant by atrial pacing at approximately postintubation values while arterial pressure was maintained within 10% of postintubation values with fluid administration or phenylephrine infusion. Overall, systemic hemodynamic changes observed during the study were similar in the two groups. Myocardial ischemic episodes were defined as a new electrocardiographic ST-segment shift of greater than or equal to 0.1 mV, new echocardiographic regional wall motion abnormalities (RWMA) and/or myocardial lactate production (MLP). A total of 18 new ischemic episodes were detected in 15 patients (7 episodes during isoflurane in 7 patients and 11 during halothane in 8 patients). Ten (56%) episodes were related to acute hemodynamic abnormalities, whereas 8 (44%) were random and unrelated to changes. Seven episodes were detected by echocardiography (38%), 6 by MLP (33%) and 1 by ECG (6%) only, whereas concomitant echocardiographic abnormalities and MLP were observed during 2 episodes (11%), echocardiographic and ECG during 1 (6%), and ECG and MLP during 1 other (6%). Ratios of regional to global coronary venous flow, coronary vascular resistance, myocardial oxygen content, and lactate extraction, along with hemodynamic data obtained during these episodes, do not support coronary steal for the development of myocardial ischemia. We conclude that in patients with steal-prone coronary anatomy anesthetized with fentanyl, neither isoflurane nor halothane administered at concentrations used in the current study is likely to cause myocardial ischemia by the coronary steal mechanism.

Asunto(s)

RESUMEN

A second-derivative synchronous scanning spectrofluorimetric method for the simultaneous determination of acetylsalicylic acid (ASA) and salicylic acid (SA) is described. The method is based on the native fluorescence of both acids in a 1% acetic acid-chloroform solution. Both ASA and SA can be determined within the concentration ranges 0.2-70 and 0.03-10 micrograms ml-1, respectively. The effect of each acid on the signal of the other has been studied in detail. Empirical equations have been used to overcome this effect, thus allowing the accurate determination of both acids in binary mixtures, without a separation step. The method has been applied to the determination of ASA and SA in blood serum and to the determination of SA impurities in aspirin formulations. Recoveries from sera spiked with both ASA (2.5-50 micrograms ml-1) and SA (100-160 micrograms ml-1) varied from 99.5 to 106.7% (mean = 102.6%) and from 93.0 to 98.0% (mean = 95.8%), respectively. Recoveries of SA from spiked aspirin solutions (0.25-1.5 mg g-1 of aspirin) varied from 98.0 to 102.0% (mean = 100.3%).

Asunto(s)

RESUMEN

The displacement of fluoride from its aluminium complexes by the action of EDTA, citrate and other ligands is a relatively slow process which can be monitored potentiometrically with a fluoride ion-selective electrode. Some characteristics of these reactions are presented. There is evidence that [AlF](2+) reacts with the competitive ligand faster than the simple free (hydrated) Al(3+) species does. The relative rates of release of fluoride by the action of various aminopolycarboxylic acids have been determined. Potentiometric reaction-rate methods have been developed for the determination of 0.2-1.5 mumole of EDTA and 0.1-1.0 mumole of citric acid, with average relative errors of approximately 3%.

RESUMEN

The pre-concentration of indole and other indolic compounds of biochemical and pharmaceutical interest at a carbon paste electrode (Nujol/graphite) has been studied. All the compounds examined can be determined, by direct voltammetric measurements in their solutions, in the concentration range 1-8 microM. Indole, methylated indoles, harmaline and serotonin were accumulated at the electrode by a combined adsorption/extraction process. By applying the medium-exchange procedure, the accumulated compounds can be determined in the same concentration range, after a 60-s pre-concentration period, enhancing, therefore, the selectivity of the voltammetric determination. A procedure for the indirect determination of L-tryptophan in serum has been developed, which is based on these findings. L-Tryptophan was cleaved to indole by tryptophanase, and indole was subsequently determined voltammetrically after a 2-min pre-concentration period at the carbon paste electrode. From 0.3 to 1.2 micrograms of L-tryptophan in a total of 75 microliters of serum sample (20-80 microM) can be determined with an average error of ca. 0.03 microgram, whereas the recovery of added L-tryptophan in serum samples is in the range 105-115%.

Asunto(s)

RESUMEN

A new titration technique is described in which the end-point is determined by measuring the relative reaction rate of the titration reaction. This technique is adequate for rather slow reactions where conventional direct titrations are not applicable. The titrations are done automatically under microcomputer control. The efficiency of this technique is demonstrated with direct titrations of certain polyhydroxy-compounds with standard periodate solution. Ethylene glycol and propylene glycol (0.05-0.3 mmole), glycerol (0.06-0.17 mmole) and mannitol (0.01-0.03 mmole) were determined with average relative errors of 0.1-0.3%.