In silico identification of tetraspanins in monopisthocotylean (Platyhelminthes: Monogenea) parasites of fish.

Tetraspanins are a superfamily of transmembrane proteins that in flatworms have structural roles in the development, maturation or stability of the tegument. Several tetraspanins are considered as potential candidates for vaccines or drugs against helminths. Monopisthocotylean monogeneans are ectoparasites of fish that are health hazards for farmed fish. The aim of this study was to identify in silico putative tetraspanins in the genomic datasets of four monopisthocotylean species. The analysis predicted and classified 40 tetraspanins in Rhabdosynochus viridisi, 39 in Scutogyrus longicornis, 22 in Gyrodactylus salaris and 13 in Neobenedenia melleni, belonging to 13 orthologous groups. The high divergence of tetraspanins made it difficult to annotate their function. However, a conserved group was identified in different metazoan taxa. According to this study, metazoan tetraspanins can be divided into 17 monophyletic groups. Of the 114 monogenean tetraspanins, only seven were phylogenetically close to tetraspanins from non-platyhelminth metazoans, which suggests that this group of proteins shows rapid sequence divergence. The similarity of the monopisthocotylean tetraspanins was highest with trematodes, followed by cestodes and then free-living platyhelminths. In total, 27 monopisthocotylean-specific and 34 flatworm-specific tetraspanins were identified. Four monogenean tetraspanins were orthologous to TSP-1, which is a candidate for the development of vaccines and a potential pharmacological target in trematodes and cestodes. Although studies of tetraspanins in parasitic flatworms are scarce, this is an interesting group of proteins for the development of new methods to control monogeneans.

Current status of precision medicine in pediatric oncology in Spain: a consensus report by the Spanish Society of Paediatric Haematology and Oncology (SEHOP).

The study analyzes the current status of personalized medicine in pediatric oncology in Spain. It gathers national data on the tumor molecular studies and genomic sequencing carried out at diagnosis and at relapse, the centers that perform these studies, the technology used and the interpretation and clinical applicability of the results. Current challenges and future directions to achieve a coordinated national personalized medicine strategy in pediatric oncology are also discussed. Next generation sequencing-based (NGS) gene panels are the technology used in the majority of centers and financial limitations are the main reason for not incorporating these studies into routine care. Nowadays, the application of precision medicine in pediatric oncology is a reality in a great number of Spanish centers. However, its implementation is uneven and lacks standardization of protocols; therefore, national coordination to overcome the inequalities is required. Collaborative work within the Personalized Medicine Group of SEHOP is an adequate framework for encouraging a step forward in the effort to move precision medicine into the national healthcare system.

Eficacia y seguridad del concentrado liofilizado de Zea mays morado en la prevención de formación de pólipos colónicos / Efficacy and safety of lyophilized concentrate purple corn (Zea mays L.) in preventing the formation of colonic polyps

RESUMEN Introducción : El cáncer colorrectal (CCR) es un problema mundial de salud pública y se origina principalmente a partir de pólipos. Hace 25 años se ha considerado una estrategia denominada quimioprevención que consiste en el consumo de alimentos como maíz morado y cúrcuma o sustancias químicas como ácido acetilsalicílico (AAS) y anti inflamatorios no esteroideos (AINEs) que previenen la carcinogénesis efectivamente al reducir el riesgo de desarrollo de pólipos. Objetivo : Determinar la eficacia y seguridad del concentrado liofilizado Zea mays morado 200 mg en la prevención de formación de pólipos colónicos en la práctica gastroenterológica privada. Material y métodos : aleatorizamos 112 pacientes (casos) para recibir este producto y 112 pacientes (controles) para recibir placebo, durante 3 años. Ambos grupos de similares características demográficas, clínicas y antecedentes patológicos. Resultados : Hallamos que los casos al final del estudio desarrollaron 83% menos pólipos que los controles (p<0,001). Los casos que desarrollaron pólipos fueron menores en número, tamaño e histología que al inicio del ensayo. Los eventos adversos que presentaron los casos fueron 4,5% similar a los controles, principalmente petequias. Conclusiones : Concluimos que el concentrado liofilizado de Zea mays morado 200 mg es eficaz y seguro en la prevención del desarrollo de pólipos colónicos.

ABSTRACT Introduction : Colorectal cancer (CRC) is a worldwide problem of public health and arises mainly from polyps. In last 25 years, a strategy called chemoprevention that consists of food intake like purple corn and turmeric or chemical substances like acetyl salicylic acid (ASA) and non-steroidal anti-inflammatory drugs (NSAIDs) that prevent effectively carcinogenesis reducing the risk of polyp development. Objective : To determine the efficacy and safety of lyophilized concentrate of purple corn (Zea mays L.) 200 mg in the prevention of colonic polyps development in private gastroenterological practice Methods : we randomly assigned 112 patients (cases) to receive this product and 112 patients (controls) to receive placebo, during 3 years. Both groups had similar demographic, clinical and medical history characteristics. Results : we found that cases developed 83% less polyps than controls (p<0.001). The cases that developed polyps were smaller in number, size and histology than at the beginning of the trial. The adverse events that cases presented were 4.5% similar to controls, mainly petechiae. Conclusion : We conclude that the lyophilized concentrate of purple corn (Zea mays L.) 200 mg was effective and safe in preventing the development of colonic polyps.

[Efficacy and safety of lyophilized concentrate purple corn (Zea mays L.) in preventing the formation of colonic polyps]. / Eficacia y seguridad del concentrado liofilizado de Zea mays morado en la prevención de formación de pólipos colónicos.

INTRODUCTION: Colorectal cancer (CRC) is a worldwide problem of public health and arises mainly from polyps. In last 25 years, a strategy called chemoprevention that consists of food intake like purple corn and turmeric or chemical substances like acetyl salicylic acid (ASA) and non-steroidal anti-inflammatory drugs (NSAIDs) that prevent effectively carcinogenesis reducing the risk of polyp development. OBJECTIVE: To determine the efficacy and safety of lyophilized concentrate of purple corn (Zea mays L.) 200 mg in the prevention of colonic polyps development in private gastroenterological practice Methods: we randomly assigned 112 patients (cases) to receive this product and 112 patients (controls) to receive placebo, during 3 years. Both groups had similar demographic, clinical and medical history characteristics. RESULTS: we found that cases developed 83% less polyps than controls (p <0.001). The cases that developed polyps were smaller in number, size and histology than at the beginning of the trial. The adverse events that cases presented were 4.5% similar to controls, mainly petechiae. CONCLUSION: We conclude that the lyophilized concentrate of purple corn (Zea mays L.) 200 mg was effective and safe in preventing the developmentof colonic polyps.

Predictors of multidrug-resistant Pseudomonas aeruginosa in neutropenic patients with bloodstream infection.

OBJECTIVES: To assess risk factors for multidrug-resistant Pseudomonas aeruginosa (MDR-PA) infection in neutropenic patients. METHODS: Single-centre retrospective analysis of consecutive bloodstream infection (BSI) episodes (2004-2017, Barcelona). Two multivariate regression models were used at BSI diagnosis and P. aeruginosa detection. Significant predictors were used to establish rules for stratifying patients according to MDR-PA BSI risk. RESULTS: Of 661 Gram-negative BSI episodes, 190 (28.7%) were caused by P. aeruginosa (70 MDR-PA). Independent factors associated with MDR-PA among Gram-negative organisms were haematological malignancy (OR 3.30; 95% CI 1.15-9.50), pulmonary source of infection (OR 7.85; 95% CI 3.32-18.56), nosocomial-acquired BSI (OR 3.52; 95% CI 1.74-7.09), previous antipseudomonal cephalosporin (OR 13.66; 95% CI 6.64-28.10) and piperacillin/tazobactam (OR 2.42; 95% CI 1.04-5.63), and BSI occurring during ceftriaxone (OR 4.27; 95% CI 1.15-15.83). Once P. aeruginosa was identified as the BSI aetiological pathogen, nosocomial acquisition (OR 7.13; 95% CI 2.87-17.67), haematological malignancy (OR 3.44; 95% CI 1.07-10.98), previous antipseudomonal cephalosporin (OR 3.82; 95% CI 1.42-10.22) and quinolones (OR 3.97; 95% CI 1.37-11.48), corticosteroids (OR 2.92; 95% CI 1.15-7.40), and BSI occurring during quinolone (OR 4.88; 95% CI 1.58-15.05) and ß-lactam other than ertapenem (OR 4.51; 95% CI 1.45-14.04) were independently associated with MDR-PA. Per regression coefficients, 1 point was assigned to each parameter, except for nosocomial-acquired BSI (3 points). In the second analysis, a score >3 points identified 60 (86.3%) out of 70 individuals with MDR-PA BSI and discarded 100 (84.2%) out of 120 with non-MDR-PA BSI. CONCLUSIONS: A simple score based on demographic and clinical factors allows stratification of individuals with bacteraemia according to their risk of MDR-PA BSI, and may help facilitate the use of rapid MDR-detection tools and improve early antibiotic appropriateness.

Calibration of a thermoluminescent dosimeter worn over lead aprons in fluoroscopy guided procedures.

Fluoroscopy guided interventional procedures provide remarkable benefits to patients. However, medical staff working near the scattered radiation field may be exposed to high cumulative equivalent doses, thus requiring shielding devices such as lead aprons and thyroid collars. In this situation, it remains an acceptable practice to derive equivalent doses to the eye lenses or other unprotected soft tissues with a dosimeter placed above these protective devices. Nevertheless, the radiation backscattered by the lead shield differs from that generated during dosimeter calibration with a water phantom. In this study, a passive personal thermoluminescent dosimeter (TLD) was modelled by means of the Monte Carlo (MC) code Penelope. The results obtained were validated against measurements performed in reference conditions in a secondary standard dosimetry laboratory. Next, the MC model was used to evaluate the backscatter correction factor needed for the case where the dosimeter is worn over a lead shield to estimate the personal equivalent dose H p (0.07) to unprotected soft tissues. For this purpose, the TLD was irradiated over a water slab phantom with a photon beam representative of the result of a fluoroscopy beam scattered by a patient. Incident beam angles of 0° and 60°, and lead thicknesses between the TLD and phantom of 0.25 and 0.5 mm Pb were considered. A backscatter correction factor of 1.23 (independent of lead thickness) was calculated comparing the results with those faced in reference conditions (i.e., without lead shield and with an angular incidence of 0°). The corrected dose algorithm was validated in laboratory conditions with dosimeters irradiated over a thyroid collar and angular incidences of 0°, 40° and 60°, as well as with dosimeters worn by interventional radiologists and cardiologists. The corrected dose algorithm provides a better approach to estimate the equivalent dose to unprotected soft tissues such as eye lenses. Dosimeters that are not shielded from backscatter radiation might underestimate personal equivalent doses when worn over a lead apron and, therefore, should be specifically characterized for this purpose.

Patient-derived xenografts for childhood solid tumors: a valuable tool to test new drugs and personalize treatments.

The use of preclinical models is essential in translational cancer research and especially important in pediatric cancer given the low incidence of each particular type of cancer. Cell line cultures have led to significant advances in cancer biology. However, cell lines have adapted to growth in artificial culture conditions, thereby undergoing genetic and phenotypic changes which may hinder the translational application. Tumor grafts developed in mice from patient tumor tissues, generally known as patient-derived xenografts (PDXs), are interesting alternative approaches to reproducing the biology of the original tumor. This review is focused on highlighting the interest of PDX models in pediatric cancer research and supporting strategies of personalized medicine. This review provides: (1) a description of the background of PDX in cancer, (2) the particular case of PDX in pediatric cancer, (3) how PDX can improve personalized medicine strategies, (4) new methods to increase engraftment, and, finally, (5) concluding remarks.

Comparison of different protocols for the extraction of microbial DNA from reef corals

This study aimed to test different protocols for the extraction of microbial DNA from the coral Mussismilia harttii. Four different commercial kits were tested, three of them based on methods for DNA extraction from soil (FastDNA SPIN Kit for soil, MP Bio, PowerSoil DNA Isolation Kit, MoBio, and ZR Soil Microbe DNA Kit, Zymo Research) and one kit for DNA extraction from plants (UltraClean Plant DNA Isolation Kit, MoBio). Five polyps of the same colony of M. harttii were macerated and aliquots were submitted to DNA extraction by the different kits. After extraction, the DNA was quantified and PCR-DGGE was used to study the molecular fingerprint of Bacteria and Eukarya. Among the four kits tested, the ZR Soil Microbe DNA Kit was the most efficient with respect to the amount of DNA extracted, yielding about three times more DNA than the other kits. Also, we observed a higher number and intensities of DGGE bands for both Bacteria and Eukarya with the same kit. Considering these results, we suggested that the ZR Soil Microbe DNA Kit is the best adapted for the study of the microbial communities of corals.

Comparison of different protocols for the extraction of microbial DNA from reef corals

This study aimed to test different protocols for the extraction of microbial DNA from the coral Mussismilia harttii. Four different commercial kits were tested, three of them based on methods for DNA extraction from soil (FastDNA SPIN Kit for soil, MP Bio, PowerSoil DNA Isolation Kit, MoBio, and ZR Soil Microbe DNA Kit, Zymo Research) and one kit for DNA extraction from plants (UltraClean Plant DNA Isolation Kit, MoBio). Five polyps of the same colony of M. harttii were macerated and aliquots were submitted to DNA extraction by the different kits. After extraction, the DNA was quantified and PCR-DGGE was used to study the molecular fingerprint of Bacteria and Eukarya. Among the four kits tested, the ZR Soil Microbe DNA Kit was the most efficient with respect to the amount of DNA extracted, yielding about three times more DNA than the other kits. Also, we observed a higher number and intensities of DGGE bands for both Bacteria and Eukarya with the same kit. Considering these results, we suggested that the ZR Soil Microbe DNA Kit is the best adapted for the study of the microbial communities of corals.

Comparison of different protocols for the extraction of microbial DNA from reef corals.

This study aimed to test different protocols for the extraction of microbial DNA from the coral Mussismilia harttii. Four different commercial kits were tested, three of them based on methods for DNA extraction from soil (FastDNA SPIN Kit for soil, MP Bio, PowerSoil DNA Isolation Kit, MoBio, and ZR Soil Microbe DNA Kit, Zymo Research) and one kit for DNA extraction from plants (UltraClean Plant DNA Isolation Kit, MoBio). Five polyps of the same colony of M. harttii were macerated and aliquots were submitted to DNA extraction by the different kits. After extraction, the DNA was quantified and PCR-DGGE was used to study the molecular fingerprint of Bacteria and Eukarya. Among the four kits tested, the ZR Soil Microbe DNA Kit was the most efficient with respect to the amount of DNA extracted, yielding about three times more DNA than the other kits. Also, we observed a higher number and intensities of DGGE bands for both Bacteria and Eukarya with the same kit. Considering these results, we suggested that the ZR Soil Microbe DNA Kit is the best adapted for the study of the microbial communities of corals.

Comparison of different protocols for the extraction of microbial DNA from reef corals

This study aimed to test different protocols for the extraction of microbial DNA from the coral Mussismilia harttii. Four different commercial kits were tested, three of them based on methods for DNA extraction from soil (FastDNA SPIN Kit for soil, MP Bio, PowerSoil DNA Isolation Kit, MoBio, and ZR Soil Microbe DNA Kit, Zymo Research) and one kit for DNA extraction from plants (UltraClean Plant DNA Isolation Kit, MoBio). Five polyps of the same colony of M. harttii were macerated and aliquots were submitted to DNA extraction by the different kits. After extraction, the DNA was quantified and PCR-DGGE was used to study the molecular fingerprint of Bacteria and Eukarya. Among the four kits tested, the ZR Soil Microbe DNA Kit was the most efficient with respect to the amount of DNA extracted, yielding about three times more DNA than the other kits. Also, we observed a higher number and intensities of DGGE bands for both Bacteria and Eukarya with the same kit. Considering these results, we suggested that the ZR Soil Microbe DNA Kit is the best adapted for the study of the microbial communities of corals.

Incidence of radiation-induced leukoencephalopathy after whole brain radiotherapy in patients with brain metastases.

INTRODUCTION: Whole brain radiation therapy (WBRT) remains a recommended treatment for patients with brain metastases in terms of symptom palliation, especially when extracranial systemic disease is present. The aim of the study was to determine the clinical correlation between pre-existing leukoaraiosis and posterior leukoencephalopathy secondary to WBRT. METHODS AND MATERIALS: We retrospectively reviewed the results of WBRT treatment in 44 patients with melanoma brain metastases. The neuroimaging abnormalities of the white matter (T2-weighted MRI) were graded over time. RESULTS: From the 37 evaluable patients the mean age was 53 years old, 23 male and 14 female. Vascular risk factors were present in 22 patients (59.5%). The WBRT total dose was 20 Gy/5fr (n=21) and 30 Gy/10fr (n=16). Leukoaraiosis pre-WBRT was observed in 9/37 patients (24.3%) and leukoencephalopathy post-WBRT in 2/37 (5.4%). Univariate analysis of prognostic factors (sex, age and vascular risk factors) for leukoaraiosis was conducted observing statistically significant differences for patients with age>or=65 years old (p=0.003). Nineteen patients survived more than 3 months. Twelve patients (63.2%) suffered from vascular risk factors. Univariate analysis demonstrated previous leukoaraiosis as a prognostic factor for developing further leukoencephalopathy after WBRT (p=0.015). CONCLUSIONS: Radiation-induced leukoencephalopathy is greater in patients with pre-existing leukoaraiosis. Because of the potential of long-term survival in a small subset of patients with brain metastases and the risk of radiation-induced dementia, neurotoxicity reduction in patients with leukoaraiosis is an important goal of treatment.

Bioremediation of a weathered and a recently oil-contaminated soils from Brazil: a comparison study.

The facility with which hydrocarbons can be removed from soils varies inversely with aging of soil samples as a result of weathering. Weathering refers to the result of biological, chemical and physical processes that can affect the type of hydrocarbons that remain in a soil. These processes enhance the sorption of hydrophobic organic contaminants (HOCs) to the soil matrix, decreasing the rate and extent of biodegradation. Additionally, pollutant compounds in high concentrations can more easily affect the microbial population of a recently contaminated soil than in a weathered one, leading to inhibition of the biodegradation process. The present work aimed at comparing the biodegradation efficiencies obtained in a recently oil-contaminated soil (spiked one) from Brazil and an weathered one, contaminated for four years, after the application of bioaugmentation and biostimulation techniques. Both soils were contaminated with 5.4% of total petroleum hydrocarbons (TPHs) and the highest biodegradation efficiency (7.4%) was reached for the weathered contaminated soil. It could be concluded that the low biodegradation efficiencies reached for all conditions tested reflect the treatment difficulty of a weathered soil contaminated with a high crude oil concentration. Moreover, both soils (weathered and recently contaminated) submitted to bioaugmentation and biostimulation techniques presented biodegradation efficiencies approximately twice as higher as the ones without the aforementioned treatment (natural attenuation).

Colonoscopía diagnóstica y terapéutica en pediatría / Diagnostic and therapeutic colonoscopy in pediatrics

La hemorragia digestiva en pediatría tiene características propias. Es una entidad poco frecuente, predominando la hemorragia digestiva alta en relación a la baja. Los pólipos en colon son la causa de hemorragia digestiva baja hasta en el 77 por ciento de los casos. La endoscopía es el método diagnóstico de elección, y de terapia que es la polipectomía. El objetivo del presente estudio es analizar las características clínicas, el diagnóstico histológico y el tratamiento instaurado. Analizamos todos los casos en que se efectuó colonoscopía en menores de 14 años, en el periodo 1990 - 1996. Se efectuaron 100 exámenes en 74 pacientes; el diagnóstico predominante fue el de pólipos (71.6 por ciento). En 14 casos se realizó mas de un estudio endoscópico, y en 16 casos se halló más de un pólipo. Dos casos tuvieron rectocolitis ulcerativa y 2 casos tuberculosis intestinal. La edad promedio fue 8.8 años. El 100 por ciento presentó rectorragia, y anemia. La localización mas frecuente fue recto y sigmoides. Se realizó polipectomía en el 94.34 por ciento de casos, siendo efectiva en el 100 por ciento, sólo hubo una complicación técnica (se enganchó el asa) que no originó morbilidad. El tipo histológico más frecuente fue el juvenil (56.66 por ciento), hallándose adenoma tubular en el 11.32 por ciento y de tipo Peutz-Jeghers en el 3.77 por ciento. La polipectomía se realizó en sala de operaciones con anestesia general en 11 casos, y en 19 se utilizó sólo sedación suave. Conclusión: Se demuestra que los pólipos son la causa más frecuente de HDB en pediatría. La colonoscopía es un método seguro de diagnóstico y tratamiento, que puede realizarse en la sala convencional de endoscopía siempre y cuando se cuente con el apoyo del anestesiólogo y/o del pediatra.

Eficacia de la asociación metoclopramida diazepamdimeticona en el sindrome dispéptico funcional (SDF). Estudio clínico randomizado controlado con placebo / Association efficacy of metoclopramide-diazepam-dimeticone in non-ulcer functional dyspepsia. Controlled clinical trial

Se estudiaron 104 pacientes ambulatorios con SDF no ulceroso, en fase sintomática, randomizados en dos grupos homogéneos:medicamento (48), placebo (56). El presente ensayo evalúa la eficacia de la asociación farmacológica de metoclopramida (5mg), diazepam (2.5mg)y dimeticona (100 mg) frente al placebo en el SDF de tipo no ulceroso, así como la tolerancia y efectos colaterales de la asociación. Luego de una apreciación inicial se realizó el seguimiento de ambos grupos durante 21 días, evaluándose:naúsea, llenura postprandial, ardor epigástrico, dolor vago, eructación, y balonamiento, y la impresión final del médico y del paciente. Todos los parámetros evaluados fueron ampliamente favorables para la asociación medicamentosa, siendo la diferencia estadísticamente significativa en el caso náusea, llenura postprandial y ardor epigástrico. La tolerancia en ambos grupos fue buena y como efectos colaterales adversos sólo cabe consignar una mayor somnolencia en el grupo medicamento, que fue mínima.

Cáncer de colon: eficacia de la radiografía a doble contraste / Colon cancer: double contrast radiography efficacy

El objetivo del presente estudio fué determinar la frecuencia en la cual una radiografía de colon a una doble contraste permite un diagnóstico correcto en el carcinoma de colon. El estudio fué hecho en el Hospital Edgardo Rebagliati Martins del IPSS en Lima. Previamente fué identificada la prevalencia el carcinoma de colon en el lugar del estudio entre 1980 y 1991, este fué 5 por ciento. Nosotros elegimos un número representativo de pacientes, 50 con un diagnóstico confirmado histopatologicamente de carcinoma de colon, en el cual una radiografía de colon a doble contraste (DC) fué hecha antes de que se hiciera el diagnóstico. El grupo control, incluyó 50 pacientes con otra patología colónica, distinta al carcinoma, en el cual una DC fué realizada previamente al diagnóstico. La sensibilidad y especificidad fueron 84 ñ 10 por ciento y 94 ñ 6 por ciento respectivamente para DC. El valor predictivo positivo fue 93 ñ 7 por ciento, y el valor predictivo negativo fué 85 ñ 10 por ciento y la eficacia 89+9 por ciento. Concluimos que la radiografía de colon a doble contraste es de gran utilidad para el diagnóstico de carcinoma de colon

Enfermedad hemorroidal: estado actual / Hemorrhoidal disease: update

En la presente revisión abordamos un tema de especial importancia que ha sido pocas veces desarrollada en la bibliografía nacional de modo integral y por el cual el gastroenterólogo y el cirujano son frecuentemente consultados. Se hace una evaluación de los conceptos tradicionales y actuales de la Enfermedad Hemorroidal, con especial énfasis en las bases anatómicas y los mecanismos fisiopatológicos implicados, una revisión de las causas y la clasificación, se resaltan las manifestaciones clínicas y métodos de evaluación y diagnóstico y se toca con especial interés el enfoque terapéutico hasta hoy desarrollado a nivel mundial. Por último, pretendemos inculcar el término de Enfermedad Hemorroidal en reemplazo del mal usado Hemorroides

Contrasting demography of two Patagonian shrubs under different conditions of sheep grazing and resource supply.

Two shrub species, dominant in western Patagonia, Argentina, exhibited different demographic behaviors under the effect of sheep grazing and of manipulated resource levels. Senecio filaginoides showed an increase in cover under increasing grazing pressures; the rise was explained by an increasing number of individuals and not by larger plants; this trend was reversed when no grazing took place. Mulinum spinosum showed a slight decrease in cover and density at increasing grazing pressures, and no change in plant size. In a field experiment in which water was added (30 mm in early summer) and the dominant grasses removed, both factors substantially augmented the number of 1-year-old seedlings of Senecio recruited; the only noticeable response of Mulinum was an increase in seedling emergence because of grass removal. Six years after this last treatment, Senecio exhibited a ten fold increase in density, and its population structure showed a peak in younger classes; Mulinum remained unaffected. In seedling surveys conducted within an exclsure and in its surroundings, the emergence of Senecio was similar in these areas in the two years of the study, whereas the emergence of Mulinum was higher inside the exclosure for one of the years. The emergence of Senecio in the wetter year was 3 times larger than in the drier one. Grazing did not affect first-year survival of any species; the major source of seedlign death in this case, as well as in the manipulative experiment, was desiccation during summer drought. We conclude that the contrasting responses of the two species to grazing are mostly due to the greater ability of Senecio to benefit from any increase in resources, including those not used by grazed plants. The difference might also be due to a reduction in the seed availability of Mulinum caused by sheep preference for its fruits. The dissimilar abilities of the two shrubs to employ the resources freed by grazing would derive more from their contrasting demographic potential (i.e. the ability to rapidly increase biomass/m2) than from a difference in their niche overlap with palatable species.