Productividad y curvas de crecimiento usando modelos no lineales en un cruce de ovino de pelo colombiano x pelibuey

Los ovinos criollos de pelo (OCP) desarrollaron ventajas adaptativas al climática tropical, que le permiten tener resistencia a enfermedades, alta fertilidad y prolificidad; sin embargo, se reportan pocas investigaciones sobre la productividad de los OCP en sistemas asociados al cultivo de la caña, lo que hace necesario realizar investigaciones, que permitan fomentar sus atributos. El objetivo del presente trabajo fue analizar la productividad y el desarrollo corporal de un cruce de OCP, mediante parámetros productivos y curvas de crecimiento. Se utilizaron 180 animales de partos simples y múltiples; se registró el peso al nacimiento (PN), al destete (PD), a los 210 días (PAJ210) y las ganancias diarias predestete (GDPRE) y posdestete (GDPOS). Los datos, se analizaron mediante estadística descriptiva, con un GLM, con los efectos sexo (S), tipo de nacimiento (TN), número de partos (NP) y época de nacimiento (EPONAC). Se emplearon los modelos no lineales Gompertz, Logístico, Brody, Richards y Von Bertalanffy, en 1.455 registros de pesos, a diferentes edades, para realizar las curvas de crecimiento. Los análisis, se efectuaron con el paquete estadístico SAS. Se consideraron los coeficientes R2, AIC y BIC, obtenidos por el método de Gauss-Newton, para seleccionar el modelo de mejor ajuste. Los machos presentaron mayores promedios en las variables PN, PD, PAJ210 y GDPOS. El TN afectó todas las variables; el PN y las GDPOS fueron afectadas por el NP y, la EPONAC, afectó PN, las GDPRE, el PAJ210 y las GDPOS. El modelo de mejor ajuste para las curvas de crecimiento fue la de Richards.

The creole hair sheep (CHS) developed adaptive advantages to the tropical climate, which allow them to have resistance to diseases, high fertility and prolificacy. Currently, there is little research on the productivity of CHS in systems associated with the cultivation of sugarcane, which makes it necessary to carry out research to promote its attributes. The purpose of this research was to analyze the productivity and body development of a crossing of CHS, using production parameters and growth curves.180 animals of single and multiple births were used; the follow weight was recorded: at birth (WB), at weaning (WW); at 210 days (W210), and furthermore, daily gains of pre-weaning (WDPRE) and post-weaning (WPPOS) were recorded. The data were analyzed using descriptive statistics with a GLM with the effects sex (S), type of birth (TB), number of births (NB) and period of birth (PB). The non-linear models Gompertz, Logistic, Brody, Richards and Von Bertalanffy were used in 1455 records of weights at different ages to perform growth curves. All analyzes were performed with the SAS statistical package. The R2, AIC and BIC coefficients obtained by the Gauss-Newton method were considered to select the best fit model. The males presented higher averages in the variables WB, WW, W210) and WPOS. The TB affected all the variables; The WB and the WPPOS were affected by the NB and the PB affected the WB, the WDPRE, the W210 and the WPPOS. The best fit model for the growth curves was of Richards.

Inhibitory Effect on Nitric Oxide Release in LPS-Stimulated Macrophages and Free Radical Scavenging Activity of Croton linearis Jacq. Leaves.

Oxidative stress is an important component of many diseases including cancer, along with inflammatory and neurodegenerative processes. Natural antioxidants have emerged as promising substances to protect the human body against reactive oxygen and nitrogen species. The present study evaluates the inhibition of nitric oxide (NO) production in LPS-stimulated RAW 264.7 murine macrophages and the free radical scavenging activity of Croton linearis Jacq. leaves. UPLC-QTOF-MS analysis identified 18 compounds: nine alkaloids with a morphinane, benzylisoquinoline or aporphine nucleus, and nine O-glycosylated-flavonoids with quercetin, kaempferol and isorhamnetin as the aglycones. The crude extract (IC50 21.59 µg/mL) and the n-hexane fraction (IC50 4.88 µg/mL) significantly reduced the NO production in LPS-stimulated macrophages but with relatively high cytotoxicity (CC50 75.30 and CC50 70.12 µg/mL, respectively), while the ethyl acetate fraction also showed good activity (IC50 40.03 µg/mL) without affecting the RAW 264.7 cell viability. On the other hand, the crude extract, as well as the dichloromethane and ethyl acetate fractions, showed better DPPH and ABTS free radical scavenging activities. Considering the chemical composition and the activity observed for Croton linearis leaves, they may be considered a good source of antioxidants to combat oxidative damage-related diseases.

Artificial Intelligence Applied to Flavonoid Data in Food Matrices.

Increasing interest in constituents and dietary supplements has created the need for more efficient use of this information in nutrition-related fields. The present work aims to obtain optimal models to predict the total antioxidant properties of food matrices, using available information on the amount and class of flavonoids present in vegetables. A new dataset using databases that collect the flavonoid content of selected foods has been created. Structural information was obtained using a structural-topological approach called TOPological Sub-Structural Molecular (TOPSMODE). Different artificial intelligence algorithms were applied, including Machine Learning (ML) methods. The study allowed us to demonstrate the effectiveness of the models using structural-topological characteristics of dietary flavonoids. The proposed models can be considered, without overfitting, effective in predicting new values of Oxygen Radical Absorption capacity (ORAC), except in the Multi-Layer Perceptron (MLP) algorithm. The best optimal model was obtained by the Random Forest (RF) algorithm. The in silico methodology we developed allows us to confirm the effectiveness of the obtained models, by introducing the new structural-topological attributes, as well as selecting those that most influence the class variable.

Electroencephalographic and peripheral temperature dynamics during a prolonged psychomotor vigilance task.

Attention lapses and fatigue are a main source of impaired performance that can lead to accidents. This study analyzed electroencephalographic (EEG) dynamics and body skin temperature as markers of attentional fluctuations in non-sleep deprived subjects during a 45min Psychomotor Vigilance Task (PVT). Independent Component Analysis and time-frequency analysis were used to evaluate the EEG data. Results showed a positive association between distal and distal-to-proximal gradient (DPG) temperatures and reaction time (RT); increments in EEG power in alpha-, theta- and beta-band frequencies in parieto-occipital, central-medial and frontal components, were associated with poor performance (slower RT) in the task. This generalized power increment fits with an increased activity in the default mode network, associated with attention lapses. This study highlights the potential use of the PVT as a tool to obtain individual physiological indices of vigilance and fatigue that could be applied to other vigilance tasks typically performed in occupational settings.

Sport participation and vigilance in children: Influence of different sport expertise.

PURPOSE: The present study aimed to investigate the relationship between different types of sport expertise (externally-paced vs. self-paced sports) and vigilance performance in children by evaluating the cardiovascular fitness level of the participants. METHODS: Three groups of children (11.0 ± 0.2 years) differentiated in terms of their regular sport participation (football players, n = 20; track and field athletes, n = 20; non-athletic controls, n = 20) took part in the study. In one session, participants performed the Leger Multi-stage fitness test to estimate their aerobic fitness level. In another session, participants completed the Psychomotor Vigilance Task (PVT) to evaluate their vigilance performance under 2 conditions of velocity demands (normal vs. speed). RESULTS: The results revealed that both groups of sport practitioners had higher cardiovascular fitness than non-athlete controls. In contrast, no significant differences in the performance PVT were found between track and field athletes and controls. Crucially, football players showed better performance in the PVT than track and field athletes and controls. These between-group differences were not modulated by the speed demands of the task. CONCLUSION: The major novel finding of this research points to a positive relationship between sport participation and vigilance performance during childhood. We discuss our results in terms of the different hypotheses put forward in the literature to explain the relationship between regular exercise and cognitive functioning: the "cardiovascular fitness" and the "cognitive component skills" hypotheses.

Electroencephalographic and skin temperature indices of vigilance and inhibitory control / Índices de la vigilancia y el control inhibitorio basados en electroencefalografía y temperatura de la piel

Neurophysiological markers of the ability to sustain attention and exert inhibitory control of inappropriate responses have usually relied on neuroimaging methods, which are not easily applicable to real-world settings. The current research tested the ability of electroencephalographic and skin temperature markers to predict performance during the Sustained Attention to Response Task (SART), which demands vigilance and inhibitory control. In Experiment 1, we recorded the electroencephalogram (EEG) during the performance of SART and found that event-related potentials underlying inhibitory control (N1 and N2/P3) were influenced by a time on task effect, suggesting a decrement in attentional resources necessary for optimal inhibitory control. In Experiments 2 and 3, we recorded skin temperatures (distal, proximal and the distal-proximal temperature gradient - DPG) and found that they were sensitive to differential demands of mental workload, and that they were related to behavioural performance in the SART. This study suggests that the recording of EEG and skin temperature may be used to monitor fluctuations of attention in natural settings, although further research should clarify the exact psychological interpretation of these physiological indices

Los marcadores neurofisiológicos de la habilidad para mantener la atención y ejercer un control inhibitorio sobre respuestas inapropiadas normalmente se han basado en métodos de neuroimagen, los cuales no son fácilmente aplicables a entornos cotidianos fuera del laboratorio. La presente investigación evaluó la habilidad de marcadores electroencefalográficos y de temperatura de la piel para predecir la ejecución durante la tarea SART (Tarea de Atención Sostenida a la Respuesta), que demanda vigilancia y control inhibitorio. En el Experimento 1, registramos el electroencefalograma (EEG) durante la ejecución de la tarea SART y encontramos que los potenciales evocados relacionados con el control inhibitorio (N1 y N2/P3) fueron influenciados por un efecto de tiempo en tarea, sugiriendo un decremento en los recursos atencionales necesarios para un control inhibitorio óptimo. En los Experimentos 2 y 3, registramos tres marcadores basados en la temperatura de la piel (zonas distal, proximal y el gradiente proximal-distal - DPG) y encontramos que fueron sensibles a las demandas diferenciales de carga de trabajo mental, que además se relacionaban con la ejecución comportamental de la SART. Este estudio sugiere que el registro del EEG y de la temperatura de la piel se pueden usar para monitorizar fluctuaciones de la atención en contextos naturales, aunque investigación posterior debería proporcionar una interpretación psicológica más precisa de estos índices fisiológicos

Blue-Enriched Light Enhances Alertness but Impairs Accurate Performance in Evening Chronotypes Driving in the Morning.

Attention maintenance is highly demanding and typically leads to vigilance decrement along time on task. Therefore, performance in tasks involving vigilance maintenance for long periods, such as driving, tends to deteriorate over time. Cognitive performance has been demonstrated to fluctuate over 24 h of the day (known as circadian oscillations), thus showing peaks and troughs depending on the time of day (leading to optimal and suboptimal times of day, respectively). Consequently, vigilance decrements are more pronounced along time on task when it is performed at suboptimal times of day. According to research, light exposure (especially blue-enriched white) enhances alertness. Thus, it has been proposed to prevent the vigilance decrement under such adverse circumstances. We aimed to explore the effects of blue-enriched white light (vs. dim light) on the performance of a simulated driving task at a suboptimal time of day. A group of evening-types was tested at 8 am, as this chronotype had previously shown their largest vigilance decrement at that time. In the dim light condition, vigilance decrements were expected on both subjective (as increments in the Karolinska Sleepiness Scale scores) and behavioral measures [as slower reaction times (RTs) in the auditory Psychomotor Vigilance Task, slower RTs to unexpected events during driving, and deteriorated driving accuracy along time on task]. Physiological activation was expected to decrease (as indexed by an increase of the distal-proximal temperature gradient, DPG). Under blue-enriched white light, all these trends should be attenuated. Results from the control dim light condition replicated the vigilance decrement in all measures. Most important, the blue-enriched white light attenuated this decrement, leading to both lower DPG and faster RTs. However, it impaired accuracy of driving performance, and did not have any effect on subjective sleepiness. We conclude that exposure to blue-enriched light provides an effective countermeasure to enhance vigilance performance at suboptimal times of day, according to measures such as RTs. However, it should be considered that alerting effects of light could impair accuracy in precision tasks as keeping a proper car position. The current findings provide ergonomic implications for safety and fatigue related management systems.

Blue-Enriched White Light Enhances Physiological Arousal But Not Behavioral Performance during Simulated Driving at Early Night.

Vigilance usually deteriorates over prolonged driving at non-optimal times of day. Exposure to blue-enriched light has shown to enhance arousal, leading to behavioral benefits in some cognitive tasks. However, the cognitive effects of long-wavelength light have been less studied and its effects on driving performance remained to be addressed. We tested the effects of a blue-enriched white light (BWL) and a long-wavelength orange light (OL) vs. a control condition of dim light on subjective, physiological and behavioral measures at 21:45 h. Neurobehavioral tests included the Karolinska Sleepiness Scale and subjective mood scale, recording of distal-proximal temperature gradient (DPG, as index of physiological arousal), accuracy in simulated driving and reaction time in the auditory psychomotor vigilance task. The results showed that BWL decreased the DPG (reflecting enhanced arousal), while it did not improve reaction time or driving performance. Instead, blue light produced larger driving errors than OL, while performance in OL was stable along time on task. These data suggest that physiological arousal induced by light does not necessarily imply cognitive improvement. Indeed, excessive arousal might deteriorate accuracy in complex tasks requiring precision, such as driving.

SNPs in bone-related miRNAs are associated with the osteoporotic phenotype.

Biogenesis and function of microRNAs can be influenced by genetic variants in the pri-miRNA sequences leading to phenotypic variability. This study aims to identify single nucleotide polymorphisms (SNPs) affecting the expression levels of bone-related mature microRNAs and thus, triggering an osteoporotic phenotype. An association analysis of SNPs located in pri-miRNA sequences with bone mineral density (BMD) was performed in the OSTEOMED2 cohort (n = 2183). Functional studies were performed for assessing the role of BMD-associated miRNAs in bone cells. Two SNPs, rs6430498 in the miR-3679 and rs12512664 in the miR-4274, were significantly associated with femoral neck BMD. Further, we measured these BMD-associated microRNAs in trabecular bone from osteoporotic hip fractures comparing to non-osteoporotic bone by qPCR. Both microRNAs were found overexpressed in fractured bone. Increased matrix mineralization was observed after miR-3679-3p inhibition in human osteoblastic cells. Finally, genotypes of rs6430498 and rs12512664 were correlated with expression levels of miR-3679 and miR-4274, respectively, in osteoblasts. In both cases, the allele that generated higher microRNA expression levels was associated with lower BMD values. In conclusion, two osteoblast-expressed microRNAs, miR-3679 and miR-4274, were associated with BMD; their overexpression could contribute to the osteoporotic phenotype. These findings open new areas for the study of bone disorders.

Intense Physical Exercise Reduces Overt Attentional Capture.

The abrupt onset of a visual stimulus typically results in overt attentional capture, which can be quantified by saccadic eye movements. Here, we tested whether attentional capture following onset of task-irrelevant visual stimuli (new object) is reduced after a bout of intense physical exercise. A group of participants performed a visual search task in two different activity conditions: rest, without any prior effort, and effort, immediately after an acute bout of intense exercise. The results showed that participants exhibited (1) slower reaction time of the first saccade toward the target when a new object was simultaneously presented in the visual field, but only in the rest activity condition, and (2) more saccades to the new object in the rest activity condition than in the effort activity condition. We suggest that immediately after an acute bout of effort, participants improved their ability to inhibit irrelevant (distracting) stimuli.

Effects of chronotype and time of day on the vigilance decrement during simulated driving.

The current study tested for the first time the effect of individual differences in circadian rhythmicity (chronotype) on both driving performance and its evolution along time on task. Morning-type and evening-type female participants were tested in morning (8 am) and evening (8 pm) sessions, in which we controlled for prior sleep duration and prior wake. Measures of body temperature, subjective activation and affect, reaction times (RT) in the Psychomotor Vigilance Task (PVT), behavioral performance (error position) and EEG alpha power during simulated driving were collected. The main result showed strong linear increments of mean and standard deviation of error position along time on task (vigilance decrement) when evening-type participants drove at their non-optimal time of day, that is, during the morning session. In contrast, driving performance in the morning-type group remained stable over time on task and was not affected by time of day. This finding can be due to differences in personality traits (e.g., conscientiousness, sensation seeking) and task appraisal associated to extreme chronotypes. The consideration of chronotype in vigilance and driving tasks can enhance safety and human performance by promoting work schedules and countermeasures to prevent failures in the accomplishment of tasks under non-optimal circadian conditions.

Additions are biased by operands: evidence from repeated versus different operands.

Recent evidence led to the conclusion that addition problems are biased towards overestimation, regardless of whether information is conveyed by symbolic or non-symbolic stimuli (the Operational Momentum effect). The present study focuses on the role of operands in the overestimation of addition problems. Based on the tie effect, and on recent evidence that the nature of operands biases addition problems towards an underestimation when operands are repeated, but towards an overestimation when different, we aim here to further elucidate the contribution of operands to addition problems. Experiment 1 replicates the underestimation of repeated-operand additions and overestimation of different-operand additions, with large numbers (around 50), and explores whether these effects also apply to small operand additions (around 10). Experiment 2 further explores the overestimation of different-operand additions by investigating the roles of operand order and numerical distance between operands. The results show that both factors have an impact on the overestimation size, but are not crucial for overestimation to occur. The results are discussed in terms of arithmetic strategies, spatial organization of numbers and magnitude representation.

[Cholangitis secondary to migrated metallic coils in the common bile duct]. / Colangitis secundaria a espirales metálicos emigrados al conducto biliar.

Biliary obstructions are infrequently caused by foreign bodies. We present an unusual case of angiographically placed metallic coils into the intrahepatic arteries to provide hemostasis, that subsequently eroded into the common bile duct leading to obstructive jaundice and cholangitis a year later. In patients with history of invasive procedures, the possibility of foreign body migration into the common bile duct should always be considered in the differential diagnosis of obstructive jaundice and cholangitis.

Colangitis secundaria a espirales metálicos emigrados al conducto biliar / [Cholangitis secondary to migrated metallic coils in the common bile duct].

Biliary obstructions are infrequently caused by foreign bodies. We present an unusual case of angiographically placed metallic coils into the intrahepatic arteries to provide hemostasis, that subsequently eroded into the common bile duct leading to obstructive jaundice and cholangitis a year later. In patients with history of invasive procedures, the possibility of foreign body migration into the common bile duct should always be considered in the differential diagnosis of obstructive jaundice and cholangitis.

Colangitis secundaria a espirales metálicos emigrados al conducto biliar. / [Cholangitis secondary to migrated metallic coils in the common bile duct].

Biliary obstructions are infrequently caused by foreign bodies. We present an unusual case of angiographically placed metallic coils into the intrahepatic arteries to provide hemostasis, that subsequently eroded into the common bile duct leading to obstructive jaundice and cholangitis a year later. In patients with history of invasive procedures, the possibility of foreign body migration into the common bile duct should always be considered in the differential diagnosis of obstructive jaundice and cholangitis.

Monoamino oxidase a: an interesting pharmacological target for the development of multi-target QSAR.

With the significant increase of life expectancy of populations in societies today, the importance of the discovery of drugs associated with neurodegenerative diseases has emerged. Therefore, neurodegenerative diseases are an important topic in Medicinal Chemistry. Although drug discovery is considered a complex and slow process, new approaches and methods have been developed with the intention of finding new chemical entities in more efficient ways. This work provides a review of virtual methodologies applied in drug discovery and especially a new model for the prediction of MAO-A inhibitors using a multi-target QSAR methodology. This model involves a mixed approach containing simple descriptors based on atom-centered fragments and functional groups (DRAGON) and topological substructural molecular design descriptors (MODESLAB). This unified multi-species QSAR model was validated through a virtual screening of a new series of oxoisoaporphine derivatives, taking into account the information in the calculated fragmental contributions. Therefore, this method represents a useful tool for the in silico screening of MAO-A inhibitors.

Gastrointestinal stromal tumors: actin expression, a new prognostic factor?

The aim of this study is to analyze the clinical outcome of gastrointestinal stromal tumors (GISTs) and to determine new prognostic factors. We perform a retrospective study of all the patients diagnosed with GIST in any location and operated on between 2000 and 2008 at our institution. We analyzed 35 patients, 16 males (45.7%) and 19 females (54.3%), with a mean age of 64 +/- 13.8 years. The tumors were located in the stomach in 22 patients (62.9%), in the small bowel in 10 (28.6%), and the retroperitoneum in three (8.6%). Referring to gastric GIST, endoscopy revealed an ulceration in the mucosa in five cases, suggesting an epithelial neoplasm. In all these cases, pathology of the biopsy specimen was nonconclusive. Survival rate at 1 and 5 years was 94.3 and 88.6 per cent, respectively. Disease-free survival at 1 and 2 years was 91.4 and 88.6 per cent, respectively. Analyzing prognostic factors, a lower disease-free survival was observed among patients with constitutional syndrome at diagnosis (P = 0.000), small bowel GIST (P = 0.037), and tumors not expressing actin (P = 0.015). A lower global survival was observed among men (P = 0,036), patients with an abdominal mass (P = 0.033) or with constitutional syndrome (P = 0.007) at diagnosis and tumors at a retroperitoneal location (P = 0.0002). Gastric GIST may be confused with epithelial neoplasms, modifying the surgery. In our patients, masculine gender, constitutional syndrome and abdominal mass at diagnosis, small bowel and retroperitoneal location, and actin negative tumors are bad prognostic factors.

Colecistitis agudas: ¿está justificado hoy en día diferir la cirugía? / Acute cholecystitis: is it still justified to delay surgery?

Introducción: El tratamiento de la colecistitis aguda puede ser inicialmente quirúrgico o conservador con cirugía posterior, revisamos los casos encontrados en nuestro centro, cómo fueron tratados y la evolución de los mismos. Material y métodos: Realizamos un estudio retrospectivo del tratamiento realizado en 178 pacientes con colecistitis aguda durante un año. Se evalúan variables relacionadas con las características de los pacientes, clínica y exploración, técnicas diagnósticas, tratamiento realizado y evolución. Resultados: El 70,2% es tratado de forma conservadora (grupo A) y el 29,8% es intervenido en las primeras 72h (grupo B). En el grupo A se trataron 96 casos con antibioterapia, 15 con antibioterapia y colecistostomía y 12 con antibioterapia y CPRE. En el grupo B se realizó colecistectomía urgente laparoscópica en el 60,4% de los casos y abierta en el 35,8%. En el grupo A el tiempo de ingreso fue de 11 días, con evolución satisfactoria en el 79,2%, tasa de mortalidad del 5,6% y tasa de reingresos del 10,7%. En el grupo B el tiempo quirúrgico fue de 111+/−43, una media de 8,7 días de ingreso, no precisaron tratamiento además de la cirugía el 68% de los casos. La evolución fue satisfactoria en todos los casos menos en 7, no hubo mortalidad en este grupo. Tuvimos una tasa de reingreso del 2%. Conclusiones: Continuamos realizando una proporción importante de tratamiento conservador en detrimento de la cirugía urgente, en números absolutos este parece tener mayor tasa de complicaciones, de mortalidad y de tiempo de ingreso hospitalario (AU)

Introduction: Acute cholecystitis treatment may initially be surgical or conservative with subsequent surgery; we reviewed the cases found in our centre, including their treatment and outcome. Material and methods: We conducted a retrospective study of treatment in 178 patients with acute cholecystitis during one year. We evaluated variables associated with patient characteristics, as well as clinical data, diagnostic tests, treatment and outcome. Results: The majority (70.2%) was treated conservatively (group A), and 29.8% were operated on in the first 72h (group B). In group A, 96 patients were treated with antibiotics, 15 with antibiotic therapy and cholecystectomy, and 12 with antibiotics and ERCP. In group B urgent laparoscopic cholecystectomy was performed in 60.4%, and 35.8% had open cholecystectomy. In group A, admission time was 11 days, with satisfactory progress in 79.2%, mortality rate of 5.6% and 10.7% of readmissions. In group B, operation time was 111 +/− 43min, a mean of 8.7 days hospital stay, and 68% of cases did not require further treatment after surgery. Outcome was satisfactory in all but 7, there was no mortality in this group. We had a return rate of 2%. Conclusions: A significant proportion of conservative treatment was carried out at the expense of emergency surgery, although in absolute numbers conservative treatment seems to have a higher rate of complications, mortality and hospitalisation time(AU)

Structural contributions of substrates to their binding to P-Glycoprotein. A TOPS-MODE approach.

A topological substructural molecular design approach (TOPS-MODE) has been used to formulate structural rules for binding of substrates of P-glycoprotein (P-gp). We first review some of the models developed in the recent literature for predicting binding to P-gp. Then, we develop a model using TOPS-MODE, which is able to identify 88.4% of substrates and 84.2% of non-substrates. When the model is presented to an external prediction set of 100 substrates and 77 nonsubstrates it identifies correctly 81.8% of all cases. Using TOPS-MODE strategy we found structural contributions for binding to P-gp, which identifies 24 structural fragments responsible for such binding. We then carried out a chemico-biological analysis of some of the structural fragments found as contributing to P-gp binding of substrates. We show that in general the model developed so far can be used as a virtual screening method for identifying substrates of P-gp from large libraries of compounds.