Examination of ionoregulatory characteristics of South American cichlids.

We examined ionoregulatory traits of four cichlid species from South America, oscars (Astronotus ocellatus), Tapajos cichlids (Geophagus sp.), Macmaster's dwarf cichlids (Apistogramma macmasteri), and keyhole cichlids (Cleithracara maronii), all inhabitants of ion-poor waters. Km values for Na+ transport in fish held in 100 µmol L-1 Na+ water ranged from 49 to 143 µmol L-1, and Jmax values spanned 450 to 1205 nmol g-1 h-1. After one month in 1000 µmol L-1 Na+ water, kinetic parameters for Na+ uptake in three of the four species acclimated, but only oscars displayed the "typical" pattern of higher Km and lower Jmax values. Low pH water inhibited Na+ uptake (JinNa) in all, and stimulated Na+ efflux (JoutNa) 2.5 to 3.5-fold in three of the four species. Oscars alone had had a measurable JinNa at pH 3.5 and no stimulation of JoutNa. We measured JinNa in oscars and keyhole cichlids during exposure to 100 µmol L-1 Ethoxzolemide (EZ), an inhibitor of carbonic anhydrase, and 1 mmol L-1 NH4Cl (HEA). EZ inhibited JinNa by about 50% and HEA reduced JinNa by 80-90%. These results suggest that Na+ uptake involves H+ extrusion. Acute exposure to 1 µmol L-1 CuSO4 and 60 nmol L-1 AgNO3 inhibited JinNa in both species by 30-85%. Exposure of oscars to 5-fold higher concentrations of both metals did not further inhibit JinNa, but it did stimulate JoutNa 50-150%. The response to metals of both species are similar to other species that have been examined.

South American characids share very similar ionoregulatory characteristics.

We examined ionoregulatory characteristics of four Characids from diverse locations in South America, emperor tetras (Nematobrycon palmeri), penguin tetras (Thayeria boehlkei), serpae tetras (Hyphessobrycon eques), and rosy tetras (Hyphessobrycon rosaceous). When held in 100 µmol L-1 Na+ water, tetras had Jmax values over 1100 nmol g-1 h-1, and Km values below 60 µmol L-1. When held in 1 mmol L-1 Na+ water kinetic parameters were unchanged. Low pH had no effect on Na+ uptake (JinNa). At pH 3.25, Na+ loss (JoutNa) was stimulated 35-85% in two of the four species. To test the linkage of JinNa to NH3 and H+ extrusion we measured JinNa during exposure to 1 mmol L-1 NH4Cl (HEA) and 100 µmol L-1 Acetazolemide (AZ). HEA stimulated JinNa of emperor tetras by 40%, but inhibited JinNa of penguin tetras by 50%; the two remaining species were unaffected. AZ (an inhibitor of carbonic anhydrase) inhibited JinNa of serpae tetras by 40%, but had no effect on the others. All tetras displayed ionoregulatory characteristics that are very similar to each other, which supports the argument that these physiological traits may be ancestral for this group and pre-date colonization of the Rio Negro. The novel finding that, Jmax and Km did not change after acclimation to 1 mM Na+ water indicates that, unlike in other species examined uptake is not plastic. The HEA and AZ results, along with pH insensitivity suggest Na+ uptake is not coupled to H+ extrusion or NH3 excretion and leaves the exact mechanism involved unclear.

Generation of multi-scroll attractors without equilibria via piecewise linear systems.

In this paper, we present a new class of dynamical system without equilibria which possesses a multiscroll attractor. It is a piecewise-linear system which is simple, stable, displays chaotic behavior and serves as a model for analogous non-linear systems. We test for chaos using the 0-1 Test for Chaos from Gottwald and Melbourne [SIAM J. Appl. Dyn. Syst. 8(1), 129-145 (2009)].

Effect of extrusion conditions on physicochemical and sensorial properties of corn-broad beans (Vicia faba) spaghetti type pasta.

Corn-broad bean spaghetti type pasta was made with a corn/broad bean flour blend in a 70:30 ratio, through an extrusion-cooking process (Brabender 10 DN single-screw extruder with a 3:1 compression ratio). The effect of temperature (T=80, 90 and 100°C) and moisture (M=28%, 31% and 34%) on the extrusion responses (specific consumption of mechanical energy and pressure) and the quality of this pasta-like product (expansion, cooking-related losses, water absorption, firmness and stickiness) was assessed. The structural changes of starch were studied by means of DSC and XRD. The extrusion-cooking process, at M=28% and T=100°C, is appropriate to obtain corn-broad bean spaghetti-type pasta with high protein and dietary fibre content and adequate quality. The cooking characteristics and resistance to overcooking depended on the degree of gelatinisation and formation of amylose-lipid complexes. The critical gelatinisation point was 46.55%; beyond that point, the quality of the product declines.

Gallbladder selection for histopathological analysis based on a simple method: a prospective comparative study.

INTRODUCTION: After a cholecystectomy, the current and traditional practice is to send each resected gallbladder to the pathologist for analysis. Some reports have suggested the possibility of selecting only those gallbladders that need to be analysed. The purpose of this study was to show a simple method for selecting which gallbladders should be sent to the pathologist. METHODS: A prospective comparative study was carried out. Two 'tests' were performed in 150 patients to detect or rule out gallbladder cancer. The first test included the patient's variables and a macroscopic gallbladder analysis performed by the surgeon (MGAS). The second test was the analysis performed by the pathologist. The results were compared. RESULTS: Of the 150 patients, 132 were women and 18 men; 130 were under 60 years old. One patient had inflammatory bowel disease, seven had changes on ultrasonography and in four cases intra-operative disturbances were observed. During the MGAS, disturbances were found in 30 patients. Eighty-one cases (54%) had at least one or more risk factors for gallbladder cancer.

Effect of the extrusion on functional properties and mineral dialyzability from Phaseolus vulgaris bean flour.

The effects of extrusion conditions on cooking degree, flour dispersion viscosity and mineral potential availability of extruded bean flour were studied. Phaseolus vulgaris beans of the agronomic cultivar "Flor de mayo" were ground and dehulled to obtain grits and then extruded at different temperatures (140, 160 and 180 degrees C) and moisture contents (17, 20 and 23%), according to a bifactorial experimental design. Degree of cooking was estimated by water solubility (WS) and specific mechanical energy (SME). The effect of variables on WS and SME were analysed by surface response methodology. Flour dispersion viscosity and mineral availability (estimated by in vitro dialyzability), were also evaluated on selected samples. Results showed that, within the ranges of the variables used for this study, only the effect of temperature was significant on the degree of cooking. No direct correlation was observed between water solubility and SME, although a maximum value of WS corresponded to a range of SME values of 400-500 J/g was observed. Dispersion viscosity decreases as WS increases, so if high calorie density is desired, for instance in order to produce a cream soup formula, bean grits should be extruded at high temperature and as low moisture as possible, in our case 180 degrees C and 17% moisture. On the other hand, the effects of extrusion variables on iron and zinc dialyzability were not much affected.

Efecto de la dureza del endospermo del maíz sobre las propiedades de hidratación y cocción / Influence of maize kernel hardness on flour hydration and cooking properties

El conocimiento acerca de la asociación entre las propiedades de cocción y la dureza del endospermo del maíz puede ayudar tanto a los nutricionistas como a los procesadores a seleccionar las materias primas para elaborar productos a base de maíz, particularmente aquellos que se consumen en forma de dispersiones cocidas. Se seleccionaron siete cultivares de maíz con distinta dureza, la que fue evaluada utilizando diferentes métodos. Los granos fueron descascarados, desgerminados y reducidos a harinas para determinar la composición, el poder de hinchamiento (PH), la solubilidad y la respuesta amilográfica. Los resultados mostraron que las diferencias en dureza de endospermo (directamente relacionada con el contenido de proteína de la harina), puede explicar las diferencias observadas tanto en el poder de hinchamiento como en los valores de consistencia amilográfica. Los cultivares de endospermo más duro muestran los menores valores de PH a alta temperatura y también los menores valores de consistencia amilográfica (viscosidad). Por el contrario los endospermos más blandos presentan los mayores valores de PH y de consistencia amilográfica. Estas diferencias son atribuidas a la restricción al hinchamiento de los gránulos del almidón que provoca la estructura de la matriz proteica. Las medida de dureza del endospermo y las de PH a 95 C pueden ser muy útiles para seleccionar cultivares que serán utilizados para lograr alimentos tales como atoles, polenta, etc.

[Influence of maize kernel hardness on flour hydration and cooking properties]. / Efecto de la dureza del endospermo del maíz sobre las propiedades de hidratación y cocción.

Knowledge of the association between cooking properties and endosperm hardness may help nutritionist and processors to select raw materials for preparing maize based food products, particularly those eaten as cooked dispersions. Seven commercial maize cultivars differing in hardness were selected to evaluate endosperm hardness on the kernels and some characteristics such as composition and hydration and cooking properties on the grits obtained from those maizes. Results show that the differences in endosperm hardness (directly related to grits protein content) can explain the differences in swelling and amylographic consistencies values. Cultivars with the hardest endosperm show the lowest values at high temperature. They also show the lowest amylographic consistencies. On the other hand softer endosperms present the highest swelling power and the highest amylographic consistencies. These differences are attributed to the restriction for starch swelling caused by the protein matrix. Endosperm hardness measurements and swelling power at 95 degrees C, can be useful to select cultivars that are going to be used to prepare maize based foods like atoles, polenta, etc.

Limited extracellular but complete intracellular acid-base regulation during short-term environmental hypercapnia in the armoured catfish, Liposarcus pardalis.

Environmental hypercapnia induces a respiratory acidosis that is usually compensated within 24-96 h in freshwater fish. Water ionic composition has a large influence on both the rate and degree of pH recovery during hypercapnia. Waters of the Amazon are characteristically dilute in ions, which may have consequences for acid-base regulation during environmental hypercapnia in endemic fishes. The armoured catfish Liposarcus pardalis, from the Amazon, was exposed to a water P(CO(2)) of 7, 14 or 42 mmHg in soft water (in micromol l(-1): Na(+), 15, Cl(-), 16, K(+), 9, Ca(2+), 9, Mg(2+), 2). Blood pH fell within 2 h from a normocapnic value of 7.90+/-0.03 to 7.56+/-0.04, 7.34+/-0.05 and 6.99+/-0.02, respectively. Only minor extracellular pH (pH(e)) recovery was observed in the subsequent 24-96 h. Despite the pronounced extracellular acidosis, intracellular pH (pH(i)) of the heart, liver and white muscle was tightly regulated within 6 h (the earliest time at which these parameters were measured) via a rapid accumulation of intracellular HCO(3)(-). While most fish regulate pH(i) during exposure to environmental hypercapnia, the time course for this is usually similar to that for pH(e) regulation. The degree of extracellular acidosis tolerated by L. pardalis, and the ability to regulate pH(i) in the face of an extracellular acidosis, are the greatest reported to date in a teleost fish. The preferential regulation of pH(i) in the face of a largely uncompensated extracellular acidosis in L. pardalis is rare among vertebrates, and it is not known whether this is associated with the ability to air-breathe and tolerate aerial exposure, or living in water dilute in counter ions, or with other environmental or evolutionary selective pressures. The ubiquity of this strategy among Amazonian fishes and the mechanisms employed by L. pardalis are clearly worthy of further study.

Protection by natural blackwater against disturbances in ion fluxes caused by low pH exposure in freshwater stingrays endemic to the Rio Negro.

Stenohaline freshwater stingrays (Potamotrygon spp.) are endemic to the very dilute (Na(+), Cl(-), Ca2(+) 300 micromol L(-1) in reference water (low DOC) to about 100 micromol L(-1) in blackwater (high DOC). In reference water, both JNain and JClin were inhibited >90%, both JNaout and JClout more than doubled, and J(Amm) did not change at pH 4.0. In blackwater, the inhibition of influxes was attenuated, the increases in outflux did not occur, and J(Amm) increased by 60% at pH 4.0. Addition of 100 micromol L(-1) Ca(2+) to reference water prevented the increases in JNaout and JClout and allowed J(Amm) to increase at pH 4.0, which demonstrates that the gills are sensitive to Ca(2+). However, addition of Ca(2+) to blackwater had no effect on the responses to pH 4.0. Addition of commercial humic acid to reference water did not duplicate the effects of natural Rio Negro blackwater at the same DOC level; instead, it greatly exacerbated the increases in JNaout and JClout at low pH and prevented any protective influence of added Ca(2+). Thus, blackwater DOC appears to be very different from commercial humic acid. Biogeochemical modeling indicated that blackwater DOC prevents Ca(2+) binding, but not H(+) binding, to the gills and that the protective effects of blackwater cannot be attributed to its higher buffer capacity or its elevated Al or Fe levels. Natural DOC may act directly at the gills at low pH to exert a protective effect and, when doing so, may override any protective action of Ca(2+) that might otherwise occur.

Mechanisms of ion transport in Potamotrygon, a stenohaline freshwater elasmobranch native to the ion-poor blackwaters of the Rio Negro.

Stingrays of the family Potamotrygonidae are the only stenohaline freshwater elasmobranchs. Potomotrygon sp. collected from the ion-poor blackwaters ([Na(+)], [Cl(-)] and [Ca(2+)]=10-30 micro mol l(-1), pH 6.1) of the Rio Negro, Amazonas, Brazil, were ammoniotelic (91% ammonia-N, 9% urea-N excretion) and exhibited blood chemistry (Na(+), Cl(-), urea, ammonia and glucose levels and osmolality) typical of freshwater teleosts. Unidirectional Na(+) and Cl(-) influx rates, measured with radiotracers, displayed saturation kinetics. The relationships for Cl(-) and Na(+) had similar K(m) values (300-500 micro mol l(-1)), but J(max) values for Cl(-) (approximately 950 micro mol kg(-1) h(-1)) were almost twice those for Na(+) (approximately 500 micro mol kg(-1) h(-1)). Cl(-) efflux rates varied with external concentration, but Na(+) efflux rates did not. There were no differences in the kinetic variables (K(m), J(max)) for influx between animals acclimated to their native ion-poor blackwater or to ion-rich hard water, but efflux rates for both Na(+) and Cl(-) were lower in the former, yielding much lower balance points (external Na(+) or Cl(-) levels at which influx and efflux were equal). Na(+), Cl(-) and Ca(2+) uptake were all strongly inhibited by acute exposure to pH 4.0, but efflux rates and Ca(2+) binding to the body surface did not change. Na(+) influx was inhibited by amiloride (10(-4) mol l(-1)) and by two of its analogs, phenamil (4 x 10(-5) mol l(-1)) and HMA (4 x 10(-5) mol l(-1)), with the latter being slightly more potent, while Cl(-) fluxes were unaffected. Cl(-) fluxes were insensitive to DIDS (2 x 10(-5) mol l(-1) or 10(-4) mol l(-1)) and SITS (10(-4) mol l(-1)), but both influx and efflux rates were strongly inhibited by DPC (10(-4) mol l(-1)) and thiocyanate (10(-4) mol l(-1)). Ammonia excretion was unresponsive to large changes in water Na(+) concentration, but was elevated by 70% during acute exposure to pH 4.0 and transiently inhibited by approximately 50% by amiloride and its analogues. The strategy of adaptation to ion-poor blackwater appears similar to that of some Rio Negro teleosts (Cichlidae) in which low-affinity transport systems are relatively sensitive to inhibition by low pH but are complemented by low diffusive loss rates. Ionic transport systems in these freshwater elasmobranchs, although superficially similar to those in some freshwater teleosts, may bear more resemblance to their presumed evolutionary precursors in marine elasmobranchs.

Diverse strategies for ion regulation in fish collected from the ion-poor, acidic Rio Negro.

We measured unidirectional ion fluxes of fish collected directly from the Rio Negro, an extremely dilute, acidic blackwater tributary of the Amazon. Kinetic analysis of Na(+) uptake revealed that most species had fairly similar J(max) values, ranging from 1,150 to 1,750 nmol g(-1) h(-1), while K(m) values varied to a greater extent. Three species had K(m) values <33 micromol L(-1), while the rest had K(m) values >or=110 micromol L(-1). Because of the extremely low Na(+) concentration of Rio Negro water, the differences in K(m) values yield very different rates of Na(+) uptake. However, regardless of the rate of Na(+) uptake, measurements of Na(+) efflux show that Na(+) balance was maintained at very low Na(+) levels (<50 micromol L(-1)) by most species. Unlike other species with high K(m) values, the catfish Corydoras julii maintained high rates of Na(+) uptake in dilute waters by having a J(max) value at least 100% higher than the other species. Corydoras julii also demonstrated the ability to modulate kinetic parameters in response to changes in water chemistry. After 2 wk in 2 mmol L(-1) NaCl, J(max) fell >50%, and K(m) dropped about 70%. The unusual acclimatory drop in K(m) may represent a mechanism to ensure high rates of Na(+) uptake on return to dilute water. As well as being tolerant of extremely dilute waters, Rio Negro fish generally were fairly tolerant of low pH. Still, there were significant differences in sensitivity to pH among the species on the basis of degree of stimulation of Na(+) efflux at low pH. There were also differences in sensitivity to low pH of Na(+) uptake, and two species maintained significant rates of uptake even at pH 3.5. When fish were exposed to low pH in Rio Negro water instead of deionized water (with the same concentrations of major ions), the effects of low pH were reduced. This suggests that high concentrations of dissolved organic molecules in the water, which give it its dark tea color, may interact with the branchial epithelium in some protective manner.

Mycotoxins inactivation by extrusion cooking of corn flour.

AIMS: To evaluate the effects of the extrusion cooking process on the inactivation of mycotoxins in corn flour. METHODS AND RESULTS: Samples of corn flour experimentally contaminated with aflatoxin B1 (AFB1) (50 ppb) and deoxynivalenol (DON) (5 ppm) were extruded. The effects of three extrusion variables (flour moisture, extrusion temperature and sodium metabisulphite addition) were analysed according to a two-level factorial design. The process was effective for the reduction of DON content (higher than 95%) under all the conditions assessed, but was only partially successful (10-25%) for the decontamination of AFB1. CONCLUSION: Extrusion cooking is effective for the inactivation of DON but is of limited value for AFB1, even if metabisulphite is added. More severe extrusion conditions are needed for the detoxification of AFB1. SIGNIFICANCE AND IMPACT OF THE STUDY: As contamination with DON occurs mainly in the field prior to harvesting and that of AFB1 is normally produced during grain storage, maize is often contaminated with DON but not with AFB1. Under these conditions, the described extrusion process can be used for the detoxification of DON. The addition of sodium metabisulphite did not significantly affect the inactivation of AFB1. Extrusion cooking is therefore an appropriate treatment for vomitoxin-contaminated maize in countries where, because of the prevailing conditions, these are the only toxins present.

[Performance of rice varieties in making bread without gluten]. / Comportamiento de variedades de arroz en la elaboración de pan sin gluten.

The objective of this work was the evaluation of the technological behavior of seven rice genotypes, using a baking test for bread without gluten, and taking account the influence of particle size and physicochemical properties of the rice on the technological aptitude to produce the bread. Total and insoluble amylose content and hydration were used to make its relationship with bread quality. The genotypes Rico and H-144-7 have contributed to give the best results at baking test while waxy rices gave the lower quality bread. Also we emphasize that a certain relationships can be assumed between hydration and insoluble amylose content with the organoleptic evaluation of breads.

Ion and acid-base balance in three species of Amazonian fish during gradual acidification of extremely soft water.

Sensitivity to acid water was assessed in three species of Amazonian fish that encounter naturally acidic blackwaters to differing degrees in the wild: tambaqui (Colossoma macropomum), matrincha (Brycon erythropterum), and tamoatá (Hoplosternum littorale), in decreasing order of occurrence in blackwater. Fish were exposed to a graded reduction in water pH, from pH 6 to 5 to 4 to 3.5, followed by return to pH 6. Fish were exposed to each new pH for 24 h. During these exposures, net transfers of ions (Na+, K+, Cl-, and Ca2+) and acid-base equivalents to and from the external water were used as physiological indicators of acid tolerance. Exposure to pH 5 had a minimal effect on net ion fluxes. Significant net losses of all ions (except Ca2+) were recorded in all three species during the first few hours of exposure to pH 4. However, ion balance was usually restored within 18 h at pH 4. Exposure to pH 3.5 caused even greater ion losses in all three species and proved to be acutely lethal to tamoatá. Matrincha sustained irreversible physiological damage at pH 3.5, as ion fluxes did not recover following return to pH 6 and there was some mortality. Tambaqui suffered the least ionoregulatory disturbances at pH 3.5 and was the only species to make a full recovery on return to pH 6. In all species, there was a tendency for ammonia excretion to increase at low water pH, but even at pH 3.5, there was no significant net uptake of acid from the water. Overall, there was a strong relationship between the magnitude of ionic disturbances and the lethality of exposure to low pH. The relative insensitivity of the ionoregulatory system of tambaqui to low pH indicates that this is a feature of fish native to blackwater systems rather than one that is common to all Amazon fish.

[Nutritional study relative to proteins, energy, and calcium in children eating school meals]. / Estudio nutricional relativo a proteínas, energía y calcio en niños que concurren a comedor escolar.

Food consumption and nutritional status were evaluated on 419 children having meals at school located in the surrounding of Santa Fe (Argentina). The protein, energy and calcium content of the meals were analyzed. Anthropometrical evaluation was made by the following indicators: weight to age, height to age and weight to height. Biochemical evaluation to a sample of the children, was made by urea/creatinine and calcium/creatinine indicators. Recommended protein consumption is achieved but a biological efficiency loss is detected, probably due to an insufficient energy intake. School meals provide about 50% of the daily energy requirements. Regarding calcium consumption, the dinner cover about 15% of the recommendations but they achieve 47-49% with the cup of milk. As in the case of energy, the calcium daily intake is insufficient as we can see by the calcium/creatinine indicator which shows that a 60% of the people are below of the normal values. All these results suggest that is necessary to increase the energy intake and calcium consumption to improve the nutritional status.

Responses of an Amazonian teleost, the tambaqui (Colossoma macropomum), to low pH in extremely soft water.

Our goal was to compare the internal physiological responses to acid challenge in an acidophilic tropical teleost endemic to dilute low-pH waters with those in nonacidophilic temperate species such as salmonids, which have been the subjects of most previous investigations. The Amazonian tambaqui (Colossoma macropomum), which migrates between circumneutral water and dilute acidic "blackwater" of the Rio Negro, was exposed to a graded low-pH and recovery regime in representative soft water (Na+ = 15, Cl- = 16, Ca2+ = 20 mumol L-1). Fish were fitted with arterial catheters for repetitive blood sampling. Water pH was altered from 6.5 (control) to 5.0, 4.0, 3.0, and back to 6.5 (recovery) on successive days. Some deaths occurred at pH 3.0. Throughout the regime, there were no disturbances of blood gases (O2 and CO2 tensions and contents) or lactate levels, and only very minor changes in acid-base status of plasma and red cells. However, erythrocytic guanylate and adenylate levels increased at pH's less than or equal to 5.0. Down to pH 4.0, plasma glucose, cortisol, and total ammonia levels remained constant, but all increased at pH 3.0, denoting a stress response. Plasma Na+ and Cl- levels declined and plasma protein concentration increased at pH 3.0, indicative of ionoregulatory and fluid volume disturbance, and neither recovered upon return to pH 6.5. Cortisol and ammonia elevations also persisted. Transepithelial potential changed progressively from highly negative values (inside) at pH 6.5 to highly positive values at pH 3.0; these alterations were fully reversible. Experimental elevations in water calcium levels drove the transepithelial potential positive at circumneutral pH, attenuated or prevented changes in transepithelial potential at low pH, and reduced Na+ and Cl- loss rates to the water during acute low-pH challenges. In general, tambaqui exhibited responses to low pH that were qualitatively similar but quantitatively more resistant than those previously documented in salmonids.

Effects of water pH and calcium concentration on ion balance in fish of the Rio Negro, Amazon.

We examined the effects of acute low-pH exposure on ion balance (Na+, Cl-, K+) in several species of fish captured from the Rio Negro, a dilute, acidic tributary of the Amazon. At pH 5.5 (untreated Rio Negro water), the four Rio Negro species tested (piranha preta, Serrasalmus rhombeus; piranha branca, Serrasalmus cf. holandi; aracu, Leporinus fasciatus; and pacu, Myleus sp.) were at or near ion balance; upon exposure to pH 3.5, while Na+ and Cl- loss rates became significant, they were relatively mild. In comparison, tambaqui (Colossoma macropomum), which were obtained from aquaculture and held and tested under the same conditions as the other fish, had loss rates seven times higher than all the Rio Negro species. At pH 3.0, rates of Na+ and Cl- loss for the Rio Negro fish increased three- to fivefold but were again much less than those observed in tambaqui. Raising water Ca2+ concentration from 10 micromol L-1 to 100 micromol L-1 during exposure to the same low pH's had no effect on rates of ion loss in the three species tested (piranha preta, piranha branca, aracu), which suggests that either they have such a high branchial affinity for Ca2+ that all sites are saturated at 10 micromol L-1 and additional Ca2+ had no effect, or that Ca2+ may not be involved in regulation of branchial ion permeability. For a final Rio Negro species, the cardinal tetra (Paracheirodon axelrodi), we monitored body Na+ concentration during 5 d of exposure to pH 6.0, 4.0, or 3.5. These pH's had no effect on body Na+ concentration. These data together suggest that exceptional acid tolerance is a general characteristic of fish that inhabit the dilute acidic Rio Negro and raise questions about the role of Ca2+ in regulation of branchial ion permeability in these fish.

[Investigation of corticospinal dysfunction in multiple sclerosis and motoneuron diseases using motor evoked potentials]. / Disfunción corticospinal en la esclerosis múltiple y en las enfermedades de la neurona motora investigada mediante potenciales evocados motores.

INTRODUCTION: The introduction of motor evoked potentials (MEP) into neurological practice has been very useful in the study of motor disorders, especially in patients with motor neurone diseases (MND) and multiple sclerosis (MS). MATERIAL AND METHODS: Forty patients with MS, twenty with MND and sixty-four apparently normal control were studied, to evaluate the use of MEP in such patients. Bilateral recordings were made from the abductor pollicis brevis and tibialis anterior. The variables studied were: cortical latency, radicular latency, central conduction time, motor excitation threshold coefficients of amplitude, duration and number of phases. RESULTS: There were significant differences in most variables when the control group and the patients were compared, and also between the two subgroups of patients (Wilk's lambda = 0.4197; p < 0.05). CA analysis significantly increased the sensitivity of the study (90.4%) with respect to analysis of latencies and central conduction times (70.4%). When analysis of the coefficients of duration and of phases was included, specificity increased by approximately 30% in both groups of patients. CONCLUSIONS: The great sensitivity of MEP as a neurophysiological diagnostic tool in investigation of corticospinal bundle lesions was demonstrated.

[Automatic anatomic-physiologic correspondence of deep structures of the central nervous system in stereotaxic functional neurosurgery]. / Automatización de la correlación anatomofisiológica de las estructuras profundas del sistema nervioso central en la neurocirugía funcional estereotáxica.

This work describes in detail the graphic facilities of a neurosurgical deep recording system for the anatomic-physiologic analysis of central nervous system deep structures in stereotaxic function neurosurgery guided by deep semi-microrecordings of the brain, as developed by the International Center of Neurologic Restoration in Cuba. This system for digitization of electrical activity in the brain uses an IBM-compatible 80386/80486 microprocessor in place of analog equipment for the visualization and recording of signals, thereby providing easier manipulation of recorded data and greater flexibility of analysis. The system automatically integrates each pulse recorded and quantifies its average amplitude. For each brain region explored, the behavior of the integrated activity recorded can be displayed on the corresponding sagittal view from the cerebral atlas of Schaltenbrand-Wahren, and then automatically scaled to the anatomic dimensions of each patient. The picture, with its different options, Facilitates analysis of anatomic correspondence of deep electrophysiologic signals so the various structures, nuclei and specific neuronal groups can be precisely located in the patient's brain. To date the system has been used successfully in over 110 neurosurgical procedures ventral intermedios (vim)-thalamotomy, pallidotomy, subthalotomy and neurotransplantation, providing more certain location of lesions or grafting sites for managing symptoms in Parkinson's disease and other movement disorders.