The mechanism of the excitatory action of catecholamines and histamine on the smooth muscle of guinea-pig ureter

1. The ionic mechanism of the excitatory action of catecholamines and histamine on the smooth muscle cells of guinea-pig ureter was studied with the double sucrose-gap method. 2. In normal conditions adrenaline and noradrenaline in a concentration of 10(-5) g/ml., and histamine in a concentration of 10(-6) g/ml., prolonged the duration of the plateau of the action potential and increased the amplitude and duration of the phasic contraction. Sometimes these changes were accompanied by a slight depolarization of the muscle membrane and by a small increase (with noradrenaline) or decrease (with histamine) of the membrane resistance. The amplitude and duration of the fast spike component of the action potential were not changed. 3. Isoprenaline in a concentration of 10(-5) g/ml. either caused no change or it decreased the duration of the plateau, reduced the amplitude of contractions and reduced excitability. 4. Tetraethyl ammonium (TEA; 5 mM), which blocks the delayed outward K current, did not prevent the increase in the duration of the plateau nor the increase of the amplitude and duration of the contractions by noradrenaline and histamine. 5. In Na-free or in K-free solution or in the presence of ouabain, i.e. in conditions in which the Na-gradient across the membrane was reduced, noradrenaline and histamine were unable to increase the duration of the plateau and the amplitude and duration of the contraction. 6. In the presence of Mn2+ (2 mM) which suppressed the spike component of tha action potential and the phasic contraction, theeffects of noradrenaline and histamine were almost abolished. 7. The results suggest a dual ionic mechanism of the alpha-action of catecholamines and of the action of histamine on the smooth muscle of ureter: (1) these drugs affect the passive ionic permeability of the membrane in a manner that results in depolarization; (2) they specifically activate the potential-dependent conductance of the slow Na channels, thereby increasing the plateau duration. The increased amplitude and duration of the contraction is the result of their primary effect on the plateau of the action potential.     

Inhibitory action of insulin-sensitizing agents on calcium channels in smooth muscle cells from resistance arteries of guinea-pig

Herein is presented the sequence of a catfish full-length p53 cDNA obtained from a cloned B cell line cDNA library. Southern blot analyses determined that a restriction fragment linked polymorphism (RFLP) existed with PstI among outbred catfish. Western blot analyses demonstrated that, when compared to PBLs, the catfish leukocyte lines express higher levels of p53 protein. Additionally, the results of Western blot analyses and in vitro translation experiments suggest that the catfish leukocyte lines may produce truncated forms of p53 due to internal initiation.     

The time course of intracellular calcium movements in single human umbilical vein smooth muscle cells

Intracellular Ca2+ ([Ca2+]i) was measured in single isolated human umbilical vein smooth muscle cells. Stimulation with histamine, in the absence of external Ca2+, mobilised Ca2+ from intracellular stores. When repeated brief applications of agonist were used, the time to onset, amplitude and rate of rise of the Ca2+ transients were found to change. Two components could often be discerned in the rising phase of the transients, an initial slow "pacemaker" and a second faster and larger component. Following the first histamine-activated transient the basal level of [Ca2+]i was invariably lower than that prior to stimulation. This lower value was maintained whilst the cell remained in Ca(2+)-free solution, but could be returned to a higher level if the cell was exposed to external Ca2+. When the mobilisation of the intracellular store was reduced to undetectable levels, re-exposure to Ca(2+)-containing medium reactivated responses. In the absence of external Ca2+, continuous application of histamine activated a series of transient increases in intracellular Ca2+, which decreased progressively in amplitude and rate of rise. The interval between transients also increased. These findings are discussed in terms of the activation of inositol trisphosphate-sensitive intracellular Ca2+ stores and their sensitivity to cytoplasmic Ca2+ and intrasarcoplasmic reticulum Ca2+.     

Oscillations of receptor-operated cationic current and internal calcium in single guinea-pig ileal smooth muscle cells

In single cells isolated from guinea-pig ileal smooth muscle, held under voltage clamp at -40 mV or -50 mV by patch pipette in the whole-cell recording mode, carbachol (CCh) evoked an oscillatory inward cationic current. The frequency of current oscillations increased with increasing CCh concentration. CCh-evoked current oscillations were followed very closely by oscillations in intracellular free Ca2+ estimated from the Indo-1 signal, and were abolished by inclusion of EGTA in the pipette solution. Ryanodine and heparin, but not nifedipine, blocked the generation of current oscillations. CCh-evoked current oscillations were abolished upon withdrawal of extracellular calcium and restored upon its reintroduction. Inclusion of GTP[gamma S] in the pipette solution caused the generation of an oscillatory inward current, which was blocked by ryanodine. The present results are consistent with the hypothesis that CCh-evoked cationic current is gated by activation of a G protein and is steeply dependent on [Ca2+]i, fluctuations in the release of Ca2+ from stores during carbachol's action produce oscillations in [Ca2+]i which cause similar oscillations in the cationic current.     

Effect of 5-hydroxytryptamine on intracellular calcium dynamics in cultured rat vascular smooth muscle cells

The present study elucidated the precise mechanism of 5-hydroxytryptamine (5-HT)-induced increase of intracellular Ca2+ concentration ([Ca2+]i) in cultured vascular smooth muscle cells isolated from rat aortic media. [Ca2+]i was measured using fluorescent Ca2+ indicator, fura-2. 5-HT caused a dose-dependent increase in [Ca2+]i, which was completely inhibited by ketanserin. alpha-Methyl-5-HT had an equipotent effect to 5-HT. Diltiazem at 10 microM partially suppressed the 5-HT-induced increase in [Ca2+]i. 5-HT also augmented Mn2+ influx, when monitored by Mn2+ quenching of fura-2 fluorescence. When extracellular Ca2+ (1.3 mM) was removed, a decrease in resting level and a small, transient increase in [Ca2+]i were observed. 5-HT stimulation also induced an increase in the production of inositol triphosphate. 5-HT-induced increase in [Ca2+]i was significantly, but partially inhibited by staurosporin and H-7. Phorbol 12-myristate 13-acetate induced an increase in [Ca2+]i, which was abolished by removal of extracellular Ca2+. 5-HT-induced increase in [Ca2+]i was not affected by the pretreatment with pertussis toxin (PTX), and was not accompanied by a change in cyclic AMP content. These results suggest that, in cultured rat aortic smooth muscle cells, 5-HT increases [Ca2+]i via 5-HT2 receptor subtype by inducing influx of extracellular Ca2+ partially through L-type voltage-dependent Ca2+ channel, as well as by mobilizing Ca2+ from its intracellular stores. Activation of protein kinase C may be positively involved in the regulatory mechanism of Ca2+ influx, but PTX-sensitive G protein and cyclic AMP seem to be not involved.     

Developmental changes in intracellular pH buffering power in smooth muscle

Hematological toxicity of tacrolimus has been rarely reported. We report two pediatric recipients of liver transplantation with anemia. They were treated with tacrolimus for 8 and 47 months, respectively, before developing pure red cell aplasia (PRCA) confirmed by bone marrow biopsy. The children recovered quickly on withdrawal of tacrolimus. The clinical profile of these children is compared with the only other patient reported in the literature with PRCA due to tacrolimus. All three patients had similar hematological findings. However, the mechanism of the tacrolimus-induced PRCA in these children appears to be different from that reported in the adult patient.     

Intermediates of prothrombin activation induce intracellular calcium mobilization in rat aortic smooth muscle cells

OBJECTIVES: To determine the diagnostic utility and net cost of magnetic resonance imaging (MRI) in the management of clinically and sonographically inconclusive scrotal lesions. METHODS: A multicenter retrospective review identified 34 patients diagnosed with scrotal MRI following inconclusive clinical and ultrasound (US) evaluation. Final diagnoses were based on surgery (n = 18) or clinical and US follow-up (n = 16). Final diagnoses of 29 testicular lesions were as follows: orchitis (n = 11), infarct (n = 6), neoplasm (n = 6), rupture (n = 3), torsion (n = 2), and radiation fibrosis (n = 1). Final diagnoses of five extratesticular lesions were as follows: epididymitis (n = 2), epididymal abscess (n = 2), and neoplasm (n = 1). Management plans prior to and following MRI findings were formulated by a general urologist and a urologic oncologist. The costs of the pre-MRI and post-MRI management plans were estimated using the Medicare reimbursement schedule. RESULTS: The leading US diagnosis was correct for 10 of 34 patients (29%) and the leading MRI diagnosis was correct for 31 of 34 patients (91%). MRI improved the management plan of the general urologist and urologic oncologist in 19 patients (56%) and 17 patients (50%), respectively. MRI worsened the management plan of both clinicians in 1 patient. Management was unchanged in all other patients. The overall net cost savings were $543 to $730 per patient for the urologic oncologist and the general urologist, respectively, and $3833 per patient originally scheduled for surgery. CONCLUSIONS: Use of MRI after inconclusive clinical and US evaluation of scrotal lesions may improve management, decrease the number of surgical procedures, and result in net cost savings.     

The effects of propofol and enflurane on single calcium channel currents of guinea-pig isolated ventricular myocytes

1. The effects of the anaesthetics, propofol (100 microM) and enflurane (3%, 1.46 mM), on single L type calcium channel currents were investigated in single myocytes isolated from guinea-pig ventricles. Channel activity was recorded from membrane patches by use of the 'cell-attached' patch-clamp technique (pipette solution containing 110 mM BaCl2, 5 microM Bay K 8644, 5 microM HEPES, pH 7.4; temperature 36 degrees C). 2. Channel conductance was calculated from the slope of the relationship between single channel current and membrane potential during step depolarizations to activate the channel over a range of approximately -20 to +20 mV. Neither propofol (6 cells) nor enflurane (7 cells) caused any significant reduction in channel conductance. 3. Both propofol (7 cells) and enflurane (9 cells) decreased the probability of the channel being open during depolarizations to +10 mV (measured from histograms of the fraction of time spent by the channel at different current levels, taking areas under the Gaussian curves fitted to the open and closed components of the distributions to represent the proportion of time spent in the two states). 4. A fraction of the current traces showed no detectable channel openings in response to step depolarizations to +10 mV. Both propofol and enflurane significantly increased the fraction of silent traces. 5. Transitions across a threshold halfway between the open and closed levels were used to define periods spent in the open and closed states. Both propofol (7 cells) and enflurane (9 cells) reduced the mean open times and increased the mean closed times of the calcium channel. 6. Histograms were plotted showing the distributions of times spent by the channels in the open and closed states. Two exponentials were fitted to the open and closed time distributions. Both propofol (7 cells) and enflurane (9 cells) shortened both time constants fitted to the open times and lengthened both time constants fitted to the closed times.7. It is concluded that both propofol and enflurane appear to alter the kinetics of opening and closing of calcium channels to favour shut channels without altering channel conductance. This effect would be expected to result in a reduction of the macroscopic calcium current and thus contribute to the negative inotropic action of these anaesthetics.     

A review of the actions and control of intracellular pH in vascular smooth muscle

OBJECTIVE: This review is an account of the physiological issues involved in the effects of pH on vascular smooth muscle tone. The following criteria were considered when reviewing the literature: (i) the type of smooth muscle, i.e. either tonic or phasic, (ii) the source of the smooth muscle i.e. pulmonary, systemic, large artery, resistance artery, vein or cell line, (iii) the effects of changing intracellular or extracellular pH alone, (iv) the acute or chronic effects of altered pH (v) the influence of extracellular pH on intracellular pH and (vi) the influence of altered intracellular pH on basal or agonist induced tone. Studies of the effects of pH on the individual intracellular components of vascular tone, specifically sarcoplasmic reticulum and contractile proteins function are considered. Finally, the pH sensitivity of molecular components that contribute to smooth muscle cell tone are reviewed. CONCLUSIONS: There appear to be distinct differences in the response of large arteries and resistance arteries to altered intracellular pH which may be based on the different properties of the smooth muscle within the wall of each blood vessel. Similarly, systemic and pulmonary vessels may respond differently, but no systematic study exists to allow a more definitive conclusion. Factors controlling intracellular pH such as intracellular buffering power and sarcolemmal pH regulating mechanisms may differ across the vascular bed and may contribute to some of the differences observed in response to altered extracellular pH. Finally, few studies have examined the pH sensitivity the intracellular processes involved in basal tone and pharmaco-mechanical coupling in vascular smooth muscle. More information concerning these latter aspects of smooth muscle function is required to progress the understanding of the modulator action on pH on vascular tone.     

Ascorbate affects proliferation of guinea-pig vascular smooth muscle cells by direct and extracellular matrix-mediated effects

Proliferation of smooth muscle cells and deposition of extracellular matrix proteins are important events in the formation of atherosclerotic plaques. We have investigated the direct and matrix-mediated effects of ascorbate on the proliferation rate of vascular smooth muscle cells (VSMC) isolated from the guinea-pig aorta. In the presence of ascorbate, cells showed a bi-phasic growth pattern. At 125 microM ascorbate, -3H--thymidine incorporation was stimulated 25%. However, higher concentrations of ascorbate gradually decreased cell-incorporated radioactivity up to 50% at 2 mM ascorbate. These effects of ascorbate on DNA synthesis in VSMC were paralleled by the changes in cell number and were not due to ascorbate cytotoxicity. Alpha-tocopherol (0.1 mM), individually and in combinations with 1 mm ascorbate, also inhibited DNA synthesis in VSMC. Ascorbate also influenced proliferation of smooth muscle cells through matrix-mediated effect. New VSMC culture plated on extracellular matrices deposited by smooth muscle cells in the presence of 0.1-1 mM ascorbate had up to 50% lower proliferation rate than on matrices from ascorbate-deficient cells, as assessed by [3H]-thymidine incorporation. This effect was independent from alpha-tocopherol and specific inhibitors of collagen synthesis: L-azetidine-2-carboxylic acid and pyridine-2,4-dicarboxylic acid. An ascorbate-dependent matrix effect was specific for smooth muscle cells grown on VSMC and human skin fibroblast-originated matrices, but not for human vascular endothelial cells. The possible involvement of ascorbate in the regulation of smooth muscle cells proliferation by its antioxidant/pro-oxidant effects and regulation of extracellular matrix composition are discussed.     

Prostaglandin production by guinea-pig endometrial cells: effects of caffeine and other modulators of intracellular calcium

The glandular epithelial cells were found to be the main source of PGF2 alpha (the uterine luteolytic hormone) in guinea-pig endometrium. There was a selective increase in PGF2 alpha production by these cells in culture at the time of the cycle (i.e. day 15) at which there is increased PGF2 alpha release from the guinea-pig uterus in vivo. TMB-8 (an intracellular calcium antagonist), W-7, trifluoperazine (both calmodulin antagonists), thapsigargin (an inhibitor of intracellular calcium uptake) and berberine (an inhibitor of calcium release) reduced the output of PGF2 alpha from day 7 glandular epithelial cells indicating that intracellular calcium is necessary for PGF2 alpha production by these cells. In contrast to its stimulatory effect on PGF2 alpha output from the guinea-pig uterus superfused in vitro and guinea-pig endometrium in culture, caffeine inhibited the output of PGF2 alpha from guinea-pig glandular epithelial cells in culture. Its effect was not fully shared by theophylline, nor mimicked by forskolin showing that cyclic AMP is not involved. The inhibitory actions of caffeine and those of the compounds which interfere with the action of intracellular calcium were not additive, suggesting that caffeine modulates the action of intracellular calcium in some way. Caffeine reduced the intracellular free calcium concentration in endometrial cells, but it was not particularly effective in this respect on day 7 glandular epithelial cells. Caffeine may therefore modulate the action of intracellular calcium in some other way.     

Interactions between membrane potential and intracellular calcium concentration in vascular smooth muscle

The intracellular calcium concentration is a major determinant of vascular tone. In the steady state it is regulated mainly by membrane potential. At the same time, several mechanisms regulating the calcium concentration, including the membrane potential, are influenced by the intracellular calcium concentration itself. There are thus multiple possible positive and negative feedback loops involved in calcium regulation. This review gives a brief overview of the different mechanisms involved, including calcium-dependent ion channels, exchangers, and ATPases, and discusses their role in agonist-mediated responses, in relation primarily to studies on the portal vein and mesenteric small arteries.     

Differential effects of etomidate, propofol, and midazolam on calcium and potassium channel currents in canine myocardial cells

BACKGROUND: Intravenous anesthetics etomidate, propofol, and midazolam produce negative inotropic effects of various degrees. The mechanism underlying these differences is largely unknown. METHODS: The effects of intravenous anesthetics on L-type Ca2+, transient outward and inward-rectifier K+ channel currents (ICa, IKto, and IK1) were compared in canine ventricular cells using the whole-cell voltage-clamp technique. ICa and IK were elicited by progressively depolarizing cells from -40 to +40 mV, and from -90 to +60 mV, respectively. The peak amplitude and time-dependent inactivation rate of ICa and IK were measured before, during, and after the administration of equimolar concentrations (5, 30, or 60 microM) of etomidate, propofol, or midazolam. RESULTS: Exposure to etomidate, propofol, and midazolam produced a concentration-dependent inhibition of ICa. Midazolam was the most potent intravenous anesthetic; at 60 microM, etomidate, propofol, and midazolam decreased peak ICa by 16 +/- 4% (mean +/- SEM), 33 +/- 5%, and 47 +/- 5%, respectively. Etomidate, propofol, and midazolam given in a 60-microM concentration decreased IKto by 8 +/- 3%, 9 +/- 2%, and 23 +/- 3%, respectively. IK1 was decreased by 60 microM etomidate and midazolam by 20 +/- 6% and 14% +/- 5%, respectively. Propofol had no effect on IK1. CONCLUSIONS: At equimolar concentrations, intravenous anesthetics decreased the peak ICa, IKto, and IK1 with various degrees of potency. Effects of anesthetics on ICa were significantly greater compared with their effects on K+ currents. These findings suggest that the negative inotropic actions of etomidate, propofol, and midazolam are related, at least in part, to decreased ICa. Some effects, such as IK inhibition, may partially antagonize effects of decreased ICa. Indeed, the final effect of these intravenous anesthetics on myocardium will be the sum of these and other sarcolemmal and intracellular effects.     

Tumor necrosis factor alpha potentiates the increase in cytosolic free calcium induced by bradykinin in guinea-pig tracheal smooth muscle cells

The ability to respond to bradykinin (BK) by a bronchospasm is one of the most intriguing characteristics observed in asthmatic patients but not in healthy subjects. The molecular basis of this sensitivity is not yet known. Therefore, we studied the effect of BK, and its putative modulation by tumor necrosis factor alpha (TNF alpha), on cytosolic free Ca2+ concentration ([Ca2+]i) in fura-2-loaded tracheal smooth muscle cells in culture. BK induced a concentration-dependent rise in [Ca2+]i at concentrations between 10(-13) and 10(-11) M which was mediated via BK receptors of the B2 subtype. The net increase in [Ca2+]i induced by 10(-12)M BK was 478 +/- 52 nM. Pre-treatment of the cells with TNF alpha (10 ng/ml) for 24 h significantly potentiated this net increase in [Ca2+]i to 956 +/- 154 nM. The presence of anti-TNF alpha antibodies inhibited this potentiation. These results show that TNF alpha is able to interact with airway smooth muscle cells which suggests the existence of receptors for TNF alpha on these cells. The study, in vivo, of such interaction should help to further elucidate the mechanisms involved in airway hyperresponsiveness.     

Effects of nicotine on K+ channel currents in vascular smooth muscle cells from rat tail arteries

Intake of nicotine has been related in many cases to acute or chronic hypertension. Using the patch-clamp technique the effect of nicotine on voltage-dependent K+ channel currents in rat tail artery smooth muscle cells was studied. Nicotine at concentrations of 1-100 microM or 0.3-3 mM increased or decreased, respectively, the amplitude of the tetraethylammonium-sensitive K+ currents. Pretreatment of cells with 10 microM dihydro-beta-erythroidine hydrobromide, a nicotinic receptor antagonist, abolished the excitatory effect (n=6), but not the inhibitory effect (n=10), of nicotine on K+ channel currents. The activation of nicotinic receptors with 100 microM 1,1-dimethyl-4-phenylpiperazinium iodide increased K+ channel currents by 27.4+/-3.8% (n=13, P < 0.01). Our results indicate that the excitatory and inhibitory effects of nicotine on K+ channels are respectively mediated by a nicotinic receptor-dependent mechanism and by a direct interaction of nicotine with K+ channels.     

Modulation of calcium and potassium currents by lamotrigine

In a prospective noninterventional study of 75 consecutive patients (mean age 71 +/- 12 years) undergoing surgery for colorectal cancer, standard postoperative energy intake was evaluated. Seventeen patients expended 40%-60% of estimated basal energy during hospitalization, 33 patients 60%-80%, 22 patients 80%-100% and three patients 100%-125%. Weight loss was observed in 67 patients (mean loss 4.7 +/- 4.4%) during hospitalization. Men had a significantly higher mean total calorie deficit (p < 0.001), and mean weight loss percentage (p < 0.01), compared to women. Preoperative nutritional status, nutrition-associated complications and length of hospital stay did not change the nutritional support and intake. Correlation analyses resulted in significant associations between gender and total calorie deficit (rs = 0.41, p < 0.01), postoperative weight loss and total calorie deficit (rs = -0.32, p < 0.01), and between postoperative weight loss and length of stay (rs = 0.27, p < 0.05). We concluded that the patients' energy intake was insufficient compared to estimated basal energy expenditure. These results suggest a need for individualized nutritional care, based on each patient's energy needs and on registration of daily calorie intake, all with the aim of increasing energy intake postoperatively in standard hospital care.     

Differential effects of organotin compounds on voltage-gated potassium currents in lymphocytes and neuroblastoma cells

BACKGROUND AND AIMS OF THE STUDY: There is no consensus over how to describe forward flow through valves in the mitral position. There are three main candidate hydraulic formulae; resistance, the Gorlin formula and the continuity equation. However, virtually no work has been performed to validate resistance and the continuity equation for valves in the mitral position. The aim of this study, therefore, was to compare the three formulae against an independent standard provided by directly observed orifice areas. MATERIALS AND METHODS: Five bioprosthetic valves with orifice areas between 0.14 cm2 and 2.33 cm2 were studied in a pulse simulator at up to 20 different stroke volume/rate combinations using quasi-physiologic flow curves. Orifice areas were measured using a video camera, pressure difference using strain gauge transducers and Doppler signals using a 1.9 MHz Pedoff probe with a Vingmed SD50 system. RESULTS: The Gorlin ratio (flow/square root of mean delta P) had a direct curvilinear relationship with the orifice area (log(y) = 0.31 + 0.36x; r = 0.94, SEE 0.08 cm2, p < 0.0001). Resistance (mean delta P/flow) had an indirect curvilinear relationship (log(y) = 0.19 - 0.55x, r = -0.93, SEE 0.13 cm2, p < 0.0001). The continuity equation was directly related to observed orifice area although with high scatter (y = 1.13 + 0.79x; r = 0.90, SEE 0.23 cm2, p < 0.0001). Although both the Gorlin ratio and resistance changed with flow, there was also a tendency for observed orifice areas to increase with flow. Empirical effective orifice areas calculated using the regression equations closely resembled observed orifice areas and agreement was reasonable, with 95% limits of -0.33 cm2 to +0.33 cm2 (Gorlin), -0.41 cm2 to +0.42 cm2 (resistance) and -0.40 cm2 to +0.48 cm2 (continuity). CONCLUSION: In conclusion, no single formula adequately predicted all observed orifice areas although resistance and the Gorlin formula gave useful predictions after empirical correction.     

Inhibitory effects of berberine on voltage- and calcium-activated potassium currents in human myeloma cells

The effects of berberine, an isoquinoline alkaloid, were investigated in human myeloma cells. In cells with intracellular Ca2+ concentration ([Ca2+]i) = 10 nM, the depolarizing square pulses from -80 mV elicited an instantaneous outward current with an inactivation. This outward current was voltage dependent, activating at -30 mV and showed inactivation with repetitive depolarization, and was hence believed to be n type voltage-activated K+ current (IK(V)). Berberine (30 microM) produced a prolongation in the recovery of IK(V) inactivation. In cells with [Ca2+]i = 1 microM, berberine also inhibited A23187-induced IK(Ca). Berberine (1-300 microM) caused the inhibition of IK(V) and IK(Ca) in the concentration-dependent manners. The IC50 values of berberine-induced inhibition of IK(V) and IK(Ca) were approximately 15 microM and 50 microM, respectively. In inside-out configurations, berberine inside the pipette suppressed the activity of K(Ca) channels without changing the single channel conductance. Berberine also inhibited the proliferation of this cell line and the IC50 value of berberine-induced inhibition of cell proliferation was 5 microM. Thus, the cytotoxic effect of berberine in cancer cells may be partially explained by its direct blockade of these K+ channels.     

Arachidonic acid-induced calcium signalling in human airway smooth muscle cells

Until now computer-assisted parasite identification was based on database applications requiring data specification on an individual basis, thus limiting the ability of the system to handle rule-based knowledge as humans are used to do. A new Expert PArasite IdentificatiON (EPAION: Greek term for expert) system was developed to serve as an interface between the database and the user, where the database is a repository for bionomic and morphological facts about the parasites for the expert system. The system was developed by using a logic-based computer language which allows the definition of rules and facts to assist the creation of queries to the database. The components of the system are the knowledge base, the multimedia data base, the inference mechanism, and the graphical user interface. The operational modules of the system are the Parasite Identifier and the system Utilities. This expert system facilitates knowledge incorporation in a manner simulating the natural mental process, thus allowing the checking of the accuracy of the information that the user feeds to the computer and the creation of intelligent queries to the database. These characteristics accelerate focusing and optimize the parasite identification scheme regardless of the user's profile of competency.