Experience in colorectal surgery at a quaternary care hospital in Bogotá, Colombia.

INTRODUCTION AND AIMS: Colorectal cancer is among the three most common cancers worldwide. Knowledge and identification of suboptimal outcome-associated factors enable comprehensive patient management. The aim of the present study was to present the results of the surgical management of colorectal cancer at a quaternary care university hospital. MATERIALS AND METHODS: An observational, analytic, cross-sectional study was conducted. Information was collected on a retrospective cohort of patients diagnosed with colorectal cancer from 2013 to 2017 at the Hospital Universitario Mayor Méderi, Bogotá, Colombia. RESULTS: Data on 452 patients, within the study period, were collected. A total of 48.5% of the patients were men, the overall complication rate was 24%, the surgical site infection (SSI) rate was 15.38%, anastomotic dehiscence occurred in 4.18% of the patients, bleeding required reoperation in 1.32%, and the intrahospital mortality rate was 7.47%. CONCLUSION: Colorectal cancer management at a university hospital was as beneficial as that provided by other types of hospitals, showing a direct association with complete R0 dissections; low complication rates, according to international reports; and reduced overall morbidity.

Assessment of metal contamination in Doñana National Park (Spain) using crayfish (Procamburus clarkii).

Water quality assessment in the Aznalcollar area was attempted using multivariate methods based on heavy metal concentrations in red swamp crayfish (Procamburus clarkii). Trace levels of four heavy metals, copper (Cu), zinc (Zn), cadmium (Cd) and lead (Pb), were detected in crayfish from eleven different stations. Principal component analysis (PCA) highlighted a gradient of contamination between the sampling stations. Cluster analysis (CA) distinguished three groups of stations. Discriminant analysis also differentiated three groups. The group centroids of the first discriminant function were used to devise an index that varies according to the source of the crayfish. These standardized values are proposed for use as a water quality index. The ability of this index to successfully predict environmental quality was proved with random samples.

Probability and amplitude of novelty responses as a function of the change in contrast of the reafferent image in G carapo.

Pulse electric fish evaluate successive electrosensory images generated by self-emitted electric discharges, creating a neural representation of the physical world. Intervals between discharges (system resolution) are controlled by a pacemaker nucleus under the influence of reafferent signals. Novel sensory stimuli cause transient accelerations of the pacemaker rate (novelty responses). This study describes quantitatively the effect of changes in contrast of reafferent electrosensory signals on the amplitude and probability of novelty responses. We found that: (i). alterations of a single image in an otherwise homogeneous series cause a novelty response; (ii). the amplitude of the elicited novelty response is a linear function of the logarithm of the change in image contrast; (iii). the parameters of this function, threshold and proportionality constant, allowed us to evaluate the transference function between change in stimulus amplitude and the amplitude of the novelty response; (iv). both parameters are independent of the baseline contrast; (v). the proportionality constant increases with the moving average of the contrast of hundreds of previous images. These findings suggest that the electrosensory system (i). calculates the difference between each reafferent electrosensory image and a neural representation of the past electrosensory input ('template'); (ii). creates the comparison template in which the relative contribution of every image decreases with the incorporation of successive images. We conclude that contrast discrimination in the electrosensory system of G. carapo obeys the general principle of appreciating any instantaneous input by the input's departure from a moving average of past images.

Dermal exposure to pesticides in greenhouses workers: discrimination and selection of variables for the design of monitoring programs.

Dermal exposure to pesticides is one of the main sanitary problems which greenhouses workers face. With the dual aims of establishing both the body part that receives the greatest exposure and the variable that has greatest influence on this exposure level, 22 pesticide application trials were performed. Trials were carried out in different greenhouse vegetable crops, using different pesticides and different spray diameters from the spray gun. In order to determine dermal exposure, the whole body method was used. Pieces of the applicator suit were subject to an extraction procedure and their pesticide content determined using GC-NPD analysis. Multivariate analysis were applied to the data obtained. Principal component analysis showed that all trials produced a high exposure level on lower left leg and lower right leg. Cluster analysis distinguished between three sample groups. The most and the least affected parts were clearly distinguished. Discriminant analysis indicated that the thin drop size of the spray gun is responsible for both the differences between groups and the minimum or maximum exposure level measured on the applicator suit. Therefore, selecting the variables, lower legs and thin drop size, is considered fundamental in designing programs for monitoring pesticide exposure.

Electroreception in Gymnotus carapo: differences between self-generated and conspecific-generated signal carriers.

Local electric fields generated by the electric organ discharge of Gymnotus carapo were explored at selected points on the skin of an emitter fish ('local self-generated fields') and on the skin of a conspecific ('local conspecific-generated fields') using a specially designed probe. Local self-generated fields showed a constant pattern along the body of the fish. At the head, these fields were collimated, much stronger than elsewhere on the fish, and had a time waveform that was site-independent. This waveform consisted of a slow head-negative wave followed by a faster head-positive wave. In contrast, time waveforms in the trunk and tail regions were site-specific, with field vectors that changed direction over time. Local conspecific-generated fields were similar to the head-to-tail field, but their spatio-temporal pattern at the skin depended on the relative orientation between the receiving fish and the emitting fish. Because self-generated fields had a slow early component at the head region, they displayed a low-frequency peak in their power spectral density histograms. In contrast, the conspecific-generated fields had time waveforms with a sharper phase reversal, resulting in a peak at higher frequency than in the self-generated field. Lesions in emitting fish demonstrated that waveform components generated by the trunk and tail regions of the electric organ predominate in conspecific-generated fields, whereas waveform components generated by the abdominal region prevail in self-generated fields. Similar results were obtained from Brachyhypopomus pinnicaudatus. These results suggest that, in pulse-emitting gymnotids, electrolocation and electrocommunication signals may be carried by different field components generated by different regions of the electric organ.

Methodological development of an index of coastal water quality: application in a tourist area.

With the aim of obtaining an index of coastal water quality, a methodological procedure based on numerical classification and discriminant analysis is presented. The procedure was applied to nutrient data (ammonia, nitrite, nitrate, and phosphate) analyzed along the coastal waters of a Spanish tourist area. Using numerical classification, three levels of nutrient loading were revealed, characterizing oligotrophic, mesotrophic, and potentially eutrophic waters. Discriminant analysis was shown to be an effective methodological tool in the discrimination between trophic groups. For every group, the discriminant procedure generated the centroids. The centroids representing oligotrophic and potentially eutrophic conditions were used to establish the two extremes of the continuum of mesotrophic conditions in these coastal waters: Standardizing values from -1 to 1, the centroids for oligotrophic and potentially eutrophic waters yielded an interval that defined the range of mesotrophic conditions. This interval is proposed as a water quality index. The ability of the coastal water quality index to successfully predict mesotrophic conditions was proved with random samples.

Application of the Kohonen neural network in coastal water management: methodological development for the assessment and prediction of water quality.

Kohonen neural network (KNN) was applied to nutrient data (ammonia, nitrite, nitrate and phosphate) taken from coastal waters in a Spanish tourist area. The activation maps obtained were not sufficient to evaluate and predict the trophic status of coastal waters. To achieve this aim, a new methodology is proposed which uses as its starting point the activation maps obtained from KNN. Firstly, to evaluate the trophic status of the coastal waters, it consists of the development of a quadrat system which enables a better classification than the traditional classification based simply on standardized data. The new classification allows clear differentiation of water quality within the mesotrophic band. Secondly, and in order to use the activation maps as predictive tools, the trophic classification, obtained from activation maps, was transposed onto new activation maps. To do this, the activation maps of the sampling points which defined each trophic group were superimposed. To avoid unnecessary complexity and to facilitate the process, this superimposition was undertaken only where the frequency exceeded 0.05. In this way, four frequency maps related to the trophic status of coastal waters (potentially eutrophic, high mesotrophic, low mesotrophic and oligotrophic) were obtained. There was no loss of relevant information in the new maps thus obtained. These frequency maps served as the basis for the successful prediction of the trophic status of random samples of coastal waters. This methodology, based on KNN, is proposed as a tool to aid the decision-making in coastal water quality management.

Electroreception in Gymnotus carapo: pre-receptor processing and the distribution of electroreceptor types.

This paper describes the peripheral mechanisms involved in signal processing of self- and conspecific-generated electric fields by the electric fish Gymnotus carapo. The distribution of the different types of tuberous electroreceptor and the occurrence of particular electric field patterns close to the body of the fish were studied. The density of tuberous electroreceptors was found to be maximal on the jaw (foveal region) and very high on the dorsal region of the snout (parafoveal region), decaying caudally. Tuberous type II electroreceptors were much more abundant than type I electroreceptors. Type I electroreceptors occurred exclusively on the head and rostral trunk regions, while type II electroreceptors were found along as much as 90 % of the fish. Electrophysiological data indicated that conspecific- and self-generated electric currents are 'funnelled' by the high conductivity and geometry of the body of the fish. These currents are concentrated at the peri-oral zone, where most electroreceptors are located. Moreover, within this region, field vector directions were collimated, constituting the most efficient stimulus for electroreceptors. It can be concluded that the passive properties of the fish tissue represent a pre-receptor device that enhances exafferent and reafferent electrical signals at the fovea-parafoveal region.

Emergency transvenous cardiac pacing placement using ultrasound guidance.

STUDY OBJECTIVE: We describe 9 patients who underwent ultrasound-guided transvenous cardiac pacing in which ultrasonographic imaging was used to assist and confirm the placement of electrode catheters within the right ventricle. METHODS: We prospectively enrolled consecutive patients with complete heart block who received emergency ultrasound-assisted transvenous cardiac pacing (TVCP). Emergency physicians performed both ultrasound scanning and placement of the TVCP electrodes at a busy urban teaching medical center. RESULTS: Real-time ultrasound-guided TVCP was successful in 8 (88.9%) of the 9 patients studied. The pacing catheter was not adequately visualized in 1 patient who ultimately required placement by a cardiologist. Echocardiography was useful in identifying pacing catheter misplacement and subsequent successful repositioning in 3 patients. CONCLUSION: Emergency physicians should be aware that ultrasound technology could be useful in assisting TVCP in the emergency department setting. Further investigation is required to adequately evaluate this modality as a new indication for ED echocardiography.