Texture differentiation using audio signal analysis with robotic interventional instruments.

Robotic minimally invasive surgery (RMIS) has played an important role in the last decades. In traditional surgery, surgeons rely on palpation using their hands. However, during RMIS, surgeons use the visual-haptics technique to compensate the missing sense of touch. Various sensors have been widely used to retrieve this natural sense, but there are still issues like integration, costs, sterilization and the small sensing area that prevent such approaches from being applied. A new method based on acoustic emission has been recently proposed for acquiring audio information from tool-tissue interaction during minimally invasive procedures that provide user guidance feedback. In this work the concept was adapted for acquiring audio information from a RMIS grasper and a first proof of concept is presented. Interactions of the grasper with various artificial and biological texture samples were recorded and analyzed using advanced signal processing and a clear correlation between audio spectral components and the tested texture were identified.

Passive artifact behavior prediction of interventional tools in high-field MRI using a 0.55T portable benchtop MR scanner.

Using magnetic resonance imaging (MRI) for guiding minimally invasive interventions requires surgical devices which on one hand are visible in the MR image but on the other hand do not generate large artifacts, which distort the overall imaging process. Passive markers are one way to visualize devices such as catheters or biopsy needles in MRI. The evaluation of newly developed passive markers usually requires access to high-field MRI scanners (1.5 T and 3 T). This makes the practical evaluation time-consuming and expensive. Hence, we propose to use a high-resolution, low field (0.55 T) benchtop MRI system to quantify the size of an artifact and to make a prediction for its corresponding size in a clinical high-field system. For the evaluation of the proposed method, catheters coated with different passive marker materials in varying concentrations were imaged in the 0. 55 T benchtop MRI scanner as well as in clinical 3 T MRI system using FLASH sequences. The experimental results revealed that an artifact prediction based on measurements in the 0. 55 T is possible for the tested marker materials. Hence, the proposed approach has a high potential for testing newly developed medical devices at a low cost, in less time and during the development process for fast feedback.

Strategies for fed-batch cultivation of t-PA producing CHO cells: substitution of glucose and glutamine and rational design of culture medium.

A strategy for fed-batch cultivation of t-PA producing recombinant CHO cells is presented, based on the substitution of glucose and glutamine for slowly metabolized nutrients and in a rational design of the medium. Media for the batch and fed stages were based on the cell specific amino acid requirements, which allowed a more accurate determination of the initiation of the fed stage and the frequency of nutrient addition from then on. Salt concentration was also reduced in both media to avoid an increase in osmolality. As a consequence of this rational design, most amino acid did not accumulate significantly during the fed stage, as usually occurs when their supply is not based on cell requirements; also, lower amounts of by-products were obtained when osmolality level was kept low, that altogether increased viability, longevity and t-PA production when compared with a reference batch culture. Alternating glucose and galactose during the fed stage, allowed lactate detoxification of the cells through their own metabolism. This allowed an increase in cell growth and cell viability with respect to a fed-batch culture in which only glucose was used in the fed stage.

Analysis of CHO cells metabolic redistribution in a glutamate-based defined medium in continuous culture.

The effect of glutamine replacement by glutamate and the balance between glutamate and glucose metabolism on the redistribution of t-PA-producing recombinant CHO cells metabolism is studied in a series of glucose shift down and shift up experiments in continuous culture. These experiments reveal the existence of multiple steady states, and experimental data are used to perform metabolic flux analysis to gain a better insight into cellular metabolism and its redistribution. Regulation of glucose feed rate promotes a higher efficiency of glucose and nitrogen source utilization, with lower production of metabolic byproducts, but this reduces t-PA specific production rate. This reduction under glucose limitation can be attributed to the fact that the cells are forced to efficiently utilize the carbon and energy source for growth, impairing the production of dispensable metabolites. It is, therefore, the combination of growth rate and carbon and energy source availability that determines the level of t-PA production in continuous culture.

Temperature optimization for reactor operation with chitin-immobilized lactase under modulated inactivation.

Temperature effects on all kinetic and inactivation parameters have been determined for chitin immobilized lactase from Kluyveromyces marxianus var. marxianus, and proper temperature functions have been validated. Maximum reaction rate, Michaelis constant referred to lactose, inhibition constant for galactose and inactivation rates increased with temperature. Enzyme inactivation was adequately modelled by a two-stage series mechanism. The effect of galactose and lactose on enzyme inactivation was determined in terms of modulation factors that were positive for galactose and negative for lactose over the whole range of temperature studied. Modulation factors were mild functions of temperature in the first stage and strong functions in the second stage of CIL inactivation where galactose positive modulation factors increase with temperature and lactose negative modulation factors decrease with temperature. Temperature explicit functions for all kinetic and inactivation parameters were incorporated into a scheme to optimize the temperature of operation for a sequential batch reactor with chitin-immobilized lactase, based on an annual cost objective function for reactor operation. Software for temperature optimization was developed creating a friendly interface with user that allows the introduction of variations in all parameters and operational criteria to perform sensitivity analysis.

Effects of a vasorelaxing factor liberated by the rat isolated atria on rat aortic rings with and without endothelium.

In 1993, Illanes et al. described a vasoactive factor, the auricular vasorelaxing factor (AVF), by controlled distension of rat isolated atria. This factor produces vasodilation, antagonizing the vasoconstrictor action of phenylephrine. We now report assays by using isolated rat aortic rings and norepinephrine as a vasoconstrictor. Isolated thoraxic aortic rings were mechanically deprived of endothelium and subjected to the effects of increasing, cumulative concentrations of 6.6 x 10(-11) M to 6.6 x 10(-7) M norepinephrine. AVF significantly decreases the constrictor effect of norepinephrine assayed afterward, shifting the vasoconstrictor dose-response relation to the right. The effect was the same in rat aortic rings with or without endothelium. Subjecting aortic rings to control vehicle samples did not alter the dose-response curve to norepinephrine. We conclude that AVF antagonizes the norepinephrine vasoconstrictor effect in rat isolated aortic rings and that the mechanism of this vasorelaxing effect is independent of any contribution from the endothelial cells.

Thermal inactivation of immobilized penicillin acylase in the presence of substrate and products.

Inactivation of immobilized penicillin acylase has been studied in the presence of substrate (penicillin G) and products (phenylacetic acid and 6-aminopenicillanic acid), under the hypothesis that substances which interact with the enzyme molecule during catalysis will have an effect on enzyme stability. The kinetics of immobilized penicillin acylase inactivation was a multistage process, decay constants being evaluated for the free-enzyme and enzyme complexes, from whose values modulation factors were determined for the effectors in each enzyme complex at each stage. 6-Aminopenicillanic acid and penicillin G stabilized the enzyme in the first stage of decay. Modulation factors in that stage were 0.96 for penicillin G and 0.98 for 6-aminopenicillanic acid. Phenylacetic acid increased the rate of inactivation in both stages, modulating factors being -2.31 and -2.23, respectively. Modulation factors influence enzyme performance in a reactor and are useful parameters for a proper evaluation.

The vascular relaxing effect of a factor released by rat atria distension.

1. In order to develop a technique to obtain and preserve the atrial natriuretic factors (ANFs) which may be useful for eventual studies on the properties of these factors, we performed experiments on rat isolated atrium. 2. The two atria of adult Wistar rats (200-300 g body wt) deprived of food and water for 48 hr, were set up in an organ bath with modified Krebs-Henseleit solution and submitted progressively to increasing tensions of 0.5, 1.5 and 3.0 g. A sample of 2 ml obtained from the bath was treated with acetic acid 1 M and kept at -12 degrees C. Within 2 days the samples were evaluated for the activity of ANFs on isolated rat aortic rings. Aortic rings previously contracted with a submaximal concentration of phenylephrine were slowly relaxed by the samples. 3. Samples from atria submitted to the highest tension shifted the dose-response curve of contraction induced by increasing cumulative doses of phenylephrine to the right. This activity was absent from samples obtained from the solution in which the atria were dissected. This experimental model allows one to obtain and preserve a vascular relaxing factor from atrial myocardium.

Evaluation of penicillin acylase production by two strains of Bacillus megaterium.

Penicillin acylase is a key enzyme for the production of semisynthetic beta-lactam antibiotics. The intracellular enzyme from Escherichia coli has been thoroughly studied and characterized. The extracellular enzyme from Bacillus megaterium, despite its potential advantages, has received less attention in the recent scientific literature. A comparative study is presented for the production of penicillin acylase with two strains of Bacillus megaterium in batch fermentation in previously optimized complex and defined media. The enzyme produced by the selected strain has been recovered, partially purified and its kinetic behaviour determined.

Solid substrate fermentation of leached beet pulp withTrichoderma aureoviride.

Optimum production of cellulases on leached beet pulp by native and mutant strains ofTrichoderma aureoviride in column-type, solid-substrate fermenters, at controlled temperature and aeration rate, was with a mutant strain, that produced 11 and 29 filter paper units of activity/g solids on raw and acid pre-treated leached beet pulp, respectively. The former value was 40% higher than in the native strain and 70% higher than in the reference strain. protein enrichment of residual solid was significant in all cases, with values up to 40% of total dry weight. Results are suitable for scale-up to pilot level.

[Immobilization of microbial lactase]. / Inmovilización de lactasa microbiana.

Lactase (beta-D galactoside-galactohydrolase, E.C.3.2.1.23) is a relevant enzyme to the dairy industry as it modifies undesirable functional and nutritional properties derived from the lactose content in milk and dairies, and as a way of recovering or upgrading cheese whey. This latter aspect has been considered to develop an enzyme catalyst suitable for the continuous hydrolysis of whey permeate. The selection of enzyme and support and the immobilization procedure has been reported previously. Results obtained in the immobilization of fungal lactase on activated chitin have prompted us to scale-up the procedure, a system being developed in which the enzyme is immobilized within the reactor (in situ). Results are presented for the in situ immobilization of lactase with and without recirculation of the reagents. Previous procedure was reproduced, although moderate profiles of activity were generated through the catalyst bed which were not eliminated by recirculation. Packed bed reactors with immobilized lactase were operated at varying flowrates and lactose concentrations, results being compared, in terms of substrate conversion and reactor productivity, with a theoretical model based on the corresponding kinetic expression and ideal flow regime. Deviations are significant at high flowrates which is attributed to backmixing and channeling through the catalyst bed. The model fits reasonably well at low flowrates and high feed substrate concentration. Productivity was 58 g of glucose/l.h at 40 ml/h of 120 g/l of lactose. Stability of the immobilized lactase was assessed in long-term reactor operation with whey permeate (35 g/l of lactose) at 40 degrees C and pH 4.0. Operational half-life was 120 days.

Internal potassium activity in ferret ventricular muscle.

Measurements of the K activity (aiK) in ferret ventricle were made using either single- or double-barrelled K-sensitive micro-electrodes. aiK was also estimated from the Nernst equation by measuring the membrane potential when changing the external K concentration. Micro-electrodes filled with the Corning K sensor gave unreliable results most probably due to interference from some substance(s) in the heart cells. Reproduceable measurements were obtained using a valinomycin cocktail as the K sensor. The mean value +/- S.D. for aiK from four experiments which met strict criteria for calibration, electrode penetration and drift was 104 mmol/l +/- 9 mmol/l. If all nine experiments were taken the value was 101 mmol/l +/- 8 mmol/l. Estimation from the Nernst equation gave values of aiK that were on average 20 mmol/l higher than the measured values with the valinomycin cocktail. It is recommended that a valinomycin cocktail be used to measure aiK.

[Protein enrichment of sugar beet bagasse for fermentation]. / Enriquecimiento proteico de bagazo de remolacha por fermentación.

Leached beet pulp is a plentiful waste in the sugar beet industry in Chile, reaching 100.000 metric tons per year on a dry basis. It represents an interesting substrate for protein upgrading through fermentation by cellulolytic organisms, because of the high content of cellulose and hemicellulose, with small amounts of protein and lignin (Table 1). The fermentation of leached beet pulp by the cellulolytic fungus Trichoderma reesei QM 9414 was studied under carbon limitation, with the celluloses as the only carbon and energy source. Nitrogen was supplied as ammonium sulphate and the medium was supplemented with other mineral salts as required for growth. Results on the kinetics of cellulose and hemicellulose degradation, level of reducing sugars in the medium, mycelial growth and production of cellulolytic enzymes are presented. Mycelial growth and related parameters were evaluated by an indirect method, based on nitrogen balances during fermentation. A yield of 0.26 g. of dry cell/g. of cellulosic substrate consumed and productivity of 0.095 g. of dry cell per liter per hour were obtained and compared with reported results on similar systems. After 40 to 45 hours of fermentation, approximately 80% of the cellulose and 45% of the hemicellulose were degraded (Fig. 2). Both, exoglucanase and endoglucanase, were induced; endoglucanase was growth associated, while exoglucanase appeared later in the growth phase, reaching its maximum activity in the stationary phase (Fig. 3). The product obtained was 30% protein and only 40 to 45% residual fiber, mostly hemicellulose. Mild acid hydrolysis has been successful in degrading hemicellulose but not cellulose, in the leached beet pulp.(ABSTRACT TRUNCATED AT 250 WORDS)

Mantencion de escorpiones en el laboratorio, orden Scorpionida, Buthidae, Rhopalurus laticauda (Thorell, 1876).Influencia de la alimentacion. / Maintenance of scorpions in the laboratory, order Scorpionida, Buthidae, Rhopalurus laticauda (Thorell, 1876).Influence of the diet

Se describe un nuevo metodo de alimentacion para alacranes (R. laticauda) en cautiverio. El metodo se basa en la administracion de un medio artificial que contiene aminoacidos, lipidos, carbohidratos, vitaminas y minerales (T. C. 199, GIBCO) y sustituye con exito a la dieta constituida por artropodos de cuerpo blando, en este caso: Blattaria, Periplaneta americana: utilizada hasta ahora por estos y otros investigadores. La dieta artificial se demuestra eficaz en la mantencion de alacranes con fines de extraccion de veneno, ya que no se observaron diferencias entre la poblacion experimental y de control en relacion a la curva de evolucion ponderal y la produccion de veneno en volumen y peso seco. Las ventajas practicas del metodo se relacionan con la ausencia del riesgo de administrar material contaminado, sea con organismos patogenos o con insecticidas o pesticidas y la facilidad de obtencion y suministro de un medio artificial, asi como la precision en cantidad y calidad de la dieta

Enriquecimiento proteico de bagazo de remolacha por fermentación. / [Protein enrichment of sugar beet bagasse for fermentation]

Leached beet pulp is a plentiful waste in the sugar beet industry in Chile, reaching 100.000 metric tons per year on a dry basis. It represents an interesting substrate for protein upgrading through fermentation by cellulolytic organisms, because of the high content of cellulose and hemicellulose, with small amounts of protein and lignin (Table 1). The fermentation of leached beet pulp by the cellulolytic fungus Trichoderma reesei QM 9414 was studied under carbon limitation, with the celluloses as the only carbon and energy source. Nitrogen was supplied as ammonium sulphate and the medium was supplemented with other mineral salts as required for growth. Results on the kinetics of cellulose and hemicellulose degradation, level of reducing sugars in the medium, mycelial growth and production of cellulolytic enzymes are presented. Mycelial growth and related parameters were evaluated by an indirect method, based on nitrogen balances during fermentation. A yield of 0.26 g. of dry cell/g. of cellulosic substrate consumed and productivity of 0.095 g. of dry cell per liter per hour were obtained and compared with reported results on similar systems. After 40 to 45 hours of fermentation, approximately 80

of the cellulose and 45

of the hemicellulose were degraded (Fig. 2). Both, exoglucanase and endoglucanase, were induced; endoglucanase was growth associated, while exoglucanase appeared later in the growth phase, reaching its maximum activity in the stationary phase (Fig. 3). The product obtained was 30

protein and only 40 to 45

residual fiber, mostly hemicellulose. Mild acid hydrolysis has been successful in degrading hemicellulose but not cellulose, in the leached beet pulp.(ABSTRACT TRUNCATED AT 250 WORDS)