Chemokine signaling via the CXCR2 receptor reinforces senescence.

Cells enter senescence, a state of stable proliferative arrest, in response to a variety of cellular stresses, including telomere erosion, DNA damage, and oncogenic signaling, which acts as a barrier against malignant transformation in vivo. To identify genes controlling senescence, we conducted an unbiased screen for small hairpin RNAs that extend the life span of primary human fibroblasts. Here, we report that knocking down the chemokine receptor CXCR2 (IL8RB) alleviates both replicative and oncogene-induced senescence (OIS) and diminishes the DNA-damage response. Conversely, ectopic expression of CXCR2 results in premature senescence via a p53-dependent mechanism. Cells undergoing OIS secrete multiple CXCR2-binding chemokines in a program that is regulated by the NF-kappaB and C/EBPbeta transcription factors and coordinately induce CXCR2 expression. CXCR2 upregulation is also observed in preneoplastic lesions in vivo. These results suggest that senescent cells activate a self-amplifying secretory network in which CXCR2-binding chemokines reinforce growth arrest.

High reproductive effort in a vulnerable lizard from high altitudes in Argentina: Reproductive biology and sexual dimorphism in Phymaturus extrilidus.

Reproductive biology is fundamental to understanding the ecology and evolution of lizards which, in turn, is essential for the definition of the species´ conservation status. We studied life-history traits related to the reproduction of the Phymaturus extrilidus lizard, including the male and female reproductive cycles, litter size, mean annual reproductive output, reproductive effort, sexual maturity size and sexual dimorphism, body condition, and fat body cycles. We found sexual dimorphism in size and shape, supporting the hypotheses of sexual and fecundity selection. Females exhibited biennial reproductive cycles synchronous with the annual prenuptial male cycle, adjusted for the maturation of the vitellogenic follicles of females. Females of P. extrilidus have the highest mean annual reproductive output (MARO=1.14) recorded in Phymaturus, and this is accompanied by the highest reproductive effort (C=0.28, C energetic =0.31). Births occur from late summer to early autumn. The female reproductive cycle, strictly biennial, like all species of the P. palluma group, and the vitellogenesis in particular, appear to be limited by body condition and the amount of fat body stored. This study presents the fundamental reproductive traits of P. extrilidus that can provide valuable information to be used in the evaluation of the conservation status of this species.

Skrjabinodon castillensis (Nematode: Pharyngodonidae) parasitizing Liolaemus gracielae lizard (Squamata: Iguania: Liolaemidae) from Argentina.

Skrjabinodon castillensis is mentioned and illustrated here, based on specimens found in the large intestines of Liolaemus gracielae (Squamata: Liolaemidae) collected in San Juan province, Argentina. The species found is assigned to Skrjabinodon based lateral alae present in males. Lateral alae beginning midway between lips and nerve ring and ending just posterior to first pair of caudal papillae. In males, caudal alae absent, paired caudal papillae present. The species recorded in this study differs from all other species assigned to Skrjabinodon by morphology and number of tail filament spines. Skrjabinodon castillensis is the ninth species from the Neotropical realm and the only species of this genus known from Argentina.

MYC directly transactivates CR2/CD21, the receptor of the Epstein-Barr virus, enhancing the viral infection of Burkitt lymphoma cells.

MYC is an oncogenic transcription factor dysregulated in about half of total human tumors. While transcriptomic studies reveal more than 1000 genes regulated by MYC, a much smaller fraction of genes is directly transactivated by MYC. Virtually all Burkitt lymphoma (BL) carry chromosomal translocations involving MYC oncogene. Most endemic BL and a fraction of sporadic BL are associated with Epstein-Barr virus (EBV) infection. The currently accepted mechanism is that EBV is the BL-causing agent inducing MYC translocation. Herein we show that the EBV receptor, CR2 (also called CD21), is a direct MYC target gene. This is based on several pieces of evidence: MYC induces CR2 expression in both proliferating and arrested cells and in the absence of protein synthesis, binds the CR2 promoter and transactivates CR2 in an E-box-dependent manner. Moreover, using mice with conditional MYC ablation we show that MYC induces CR2 in primary B cells. Importantly, modulation of MYC levels directly correlates with EBV's ability of infection in BL cells. Altogether, in contrast to the widely accepted hypothesis for the correlation between EBV and BL, we propose an alternative hypothesis in which MYC dysregulation could be the first event leading to the subsequent EBV infection.

SKP2 oncogene is a direct MYC target gene and MYC down-regulates p27(KIP1) through SKP2 in human leukemia cells.

SKP2 is the ubiquitin ligase subunit that targets p27(KIP1) (p27) for degradation. SKP2 is induced in the G(1)-S transit of the cell cycle, is frequently overexpressed in human cancer, and displays transformation activity in experimental models. Here we show that MYC induces SKP2 expression at the mRNA and protein levels in human myeloid leukemia K562 cells with conditional MYC expression. Importantly, in these systems, induction of MYC did not activate cell proliferation, ruling out SKP2 up-regulation as a consequence of cell cycle entry. MYC-dependent SKP2 expression was also detected in other cell types such as lymphoid, fibroblastic, and epithelial cell lines. MYC induced SKP2 mRNA expression in the absence of protein synthesis and activated the SKP2 promoter in luciferase reporter assays. With chromatin immunoprecipitation assays, MYC was detected bound to a region of human SKP2 gene promoter that includes E-boxes. The K562 cell line derives from human chronic myeloid leukemia. In a cohort of chronic myeloid leukemia bone marrow samples, we found a correlation between MYC and SKP2 mRNA levels. Analysis of cancer expression databases also indicated a correlation between MYC and SKP2 expression in lymphoma. Finally, MYC-induced SKP2 expression resulted in a decrease in p27 protein in K562 cells. Moreover, silencing of SKP2 abrogated the MYC-mediated down-regulation of p27. Our data show that SKP2 is a direct MYC target gene and that MYC-mediated SKP2 induction leads to reduced p27 levels. The results suggest the induction of SKP2 oncogene as a new mechanism for MYC-dependent transformation.

Skrjabinodon castillensis n. sp. (Nematoda:Pharyngodonidae) from the Homonota horrida and H.darwinii (Squamata: Phyllodactylidae) from Argentina and key for the Neotropical species of the genus Skrjabinodon.

Skrjabinodon castillensis n. sp. is described and illustrated here, based on specimens found in the large intestines of Homonota horrida (province San Juan) and Homonota darwinii (province Neuquén) (Squamata: Phyllodactylidae) from Argentina. The new species is assigned to Skrjabinodon based lateral alae present in males, absent in females. Lateral alae beginning midway between lips and nerve ring and ending just posterior to first pair of caudal papillae. Females with vulva near esophageal bulb. In males, caudal alae absent, paired caudal papillae present. Skrjabinodon castillensis n. sp. represents the 9th species from the Neotropical realm. The new species differs from all other species assigned to Skrjabinodon by morphology of tail filament and number of tail filament spines. Skrjabinodon castillensis n. sp. is the only species of this genus known from Argentina. A key to the species of Skrjabinodon in the Neotropical realm is provided.

Gestational diabetes mellitus alters maternal and neonatal circulating endothelial progenitor cell subsets.

OBJECTIVE: The purpose of this study was to examine whether women with gestational diabetes mellitus (GDM) and their offspring have reduced endothelial progenitor cell subsets and vascular reactivity. STUDY DESIGN: Women with GDM, healthy control subjects, and their infants participated. Maternal blood and cord blood were assessed for colony-forming unit-endothelial cells and endothelial progenitor cell subsets with the use of polychromatic flow cytometry. Cord blood endothelial colony-forming cells were enumerated. Vascular reactivity was tested by laser Doppler imaging. RESULTS: Women with GDM had fewer CD34, CD133, CD45, and CD31 cells (circulating progenitor cells [CPCs]) at 24-32 weeks' gestation and 1-2 days after delivery, compared with control subjects. No differences were detected in colony-forming unit-endothelial cells or colony-forming unit-endothelial cells. In control subjects, CPCs were higher in the third trimester, compared with the postpartum period. Cord blood from GDM pregnancies had reduced CPCs. Vascular reactivity was not different between GDM and control subjects. CONCLUSION: The normal physiologic increase in CPCs during pregnancy is impaired in women with GDM, which may contribute to endothelial dysfunction and GDM-associated morbidities.

Offseason Medfly Trapping Using Makeshift Fruit-Based and Wine Vinegar Baits.

Development of cost-effective traps and attractants is important for sustainable pest management. In the case of the Medfly, Ceratitis capitata Wiedemann, a worldwide pest of fruit production, recent interest in development of mass trapping strategies and low-cost easy-to-get artisanal traps for resource poor grower use has prompted renewed interest in research on attractants and traps. Additionally, such interest is also rooted on the need for effective female attractants to monitor wild population dynamics under male-only sterile fly releases. Response of wild flies and sterile males to makeshift traps (modified polyethylene terephthalate (pet) bottles) baited with fruit juice and wine vinegar dilutions with and without the addition of sugar revealed that a 50% dilution of wine vinegar or sweetened orange juice were more attractive than the standard Torula baits during the offseason (after harvest) in a peach orchard in arid irrigated valleys of San Juan Argentina. Such results suggest that volatiles from orange peel and juice are good candidates for development of Medfly attractants, and that pet bottles baited with sweetened orange juice and wine vinegar may be used by small growers and homeowners as low-cost-effective traps for Medfly control. Our results also suggest that Medfly response to food-based and fruit-based volatiles may be seasonally dynamic, a finding with important pest management implications.

Checklist of nematode parasites of reptiles from Argentina.

A summary of the parasitic nematodes of reptiles from Argentina is presented. It is a compilation of 29 parasitological papers published between 1992 and May 2020. This review includes information about 40 species of reptiles (4 snakes, 3 turtles, 1 anfisbaenian and 32 lizards). Twenty-six nematodes species have been reported from reptiles. The present review provides data on hosts, geographical distribution and site of infection. A host/parasite list is also provided.

New association between Amblyomma parvitarsum (Acari: Ixodidae) and the endemic lizard Liolaemus eleodori (Iguania: Liolaemidae) in Argentina

Records of lizard parasitizing ticks in Argentina are scarce and incomplete. We recorded a new population of Liolaemus eleodori, a lizard endemic to Argentina, parasitized by the hard tick Amblyomma parvitarsum. Hence, the objective of this study is to report this new association and enhance knowledge about its parasitism on reptiles of Argentina. To do this, we researched ectoparasitic loads. We determined different ecological predictors: intensity, mean intensity and prevalence. Our results provide the first data on the parasitism of nymphal stages on this lizard. We found a tick prevalence of 91.6% and a mean intensity of 2.45. Considering sexes, mean intensity was higher in females than in males. The gular region and lower ventral abdomen were the highest parasitized anatomical regions. This new record of the host-parasite association suggests that this relationship is not accidental, with this lizard species being central to the tick's life cycle. Probably, the microhabitat of this lizard species is essential for the tick to reach high prevalence. Our study represents an important contribution and provides additional information on parasitism in lizards of Argentina.

Myc stimulates cell cycle progression through the activation of Cdk1 and phosphorylation of p27.

Cell cycle stimulation is a major transforming mechanism of Myc oncoprotein. This is achieved through at least three concomitant mechanisms: upregulation of cyclins and Cdks, downregulation of the Cdk inhibitors p15 and p21 and the degradation of p27. The Myc-p27 antagonism has been shown to be relevant in human cancer. To be degraded, p27 must be phosphorylated at Thr-187 to be recognized by Skp2, a component of the ubiquitination complex. We previously described that Myc induces Skp2 expression. Here we show that not only Cdk2 but Cdk1 phosphorylates p27 at the Thr-187. Moreover, Myc induced p27 degradation in murine fibroblasts through Cdk1 activation, which was achieved by Myc-dependent cyclin A and B induction. In the absence of Cdk2, p27 phosphorylation at Thr-187 was mainly carried out by cyclin A2-Cdk1 and cyclin B1-Cdk1. We also show that Cdk1 inhibition was enough for the synthetic lethal interaction with Myc. This result is relevant because Cdk1 is the only Cdk strictly required for cell cycle and the reported synthetic lethal interaction between Cdk1 and Myc.

Insulin-like growth factor I in sera, ovarian follicles and follicular fluid of cows with spontaneous or induced cystic ovarian disease.

The objective of this research was to determine changes in IGF-I levels in serum and follicular fluid, and immunoreactivity of the follicle wall of cows with spontaneous (slaughter specimens) or ACTH-induced follicular cysts, and to compare results to normal cycling (control) cows after selection of the ovulatory follicle. Concentrations of IGF-I in serum did not differ between control and cystic animals (p=0.76). Fluid from the ovulatory follicle in control cows had 41% higher concentrations of IGF-I than that from cystic follicles collected at slaughter (spontaneous cysts; p<0.05) and 70% higher than that in induced follicular cysts (p<0.05). An intense positive immunostaining with anti-IGF-I was observed in granulosa cells (p<0.05) and in the theca interna (p<0.05) of secondary and tertiary follicles in all three groups of animals, but staining was less intense in cystic (p<0.05) and atretic follicles (p<0.05). This study provides evidence to suggest that cystic ovarian disease in cattle is associated with decreased concentrations of IGF-I in follicular fluid, but not in serum, and decreased production of IGF-I in the follicular wall. These data support the notion that IGF-I plays a role in the regulation of folliculogenesis, and may participate in the pathogenesis of cystic ovarian disease in cattle.

Inhibitory effect of c-Myc on p53-induced apoptosis in leukemia cells. Microarray analysis reveals defective induction of p53 target genes and upregulation of chaperone genes.

We have previously demonstrated that c-Myc impairs p53-mediated apoptosis in K562 human leukemia cells, which lack ARF. To investigate the mechanisms by which c-Myc protects from p53-mediated apoptosis, we used K562 cells that conditionally express c-Myc and harbor a temperature-sensitive allele of p53. Gene expression profiles of cells expressing wild-type conformation p53 in the presence of either uninduced or induced c-Myc were analysed by cDNA microarrays. The results show that multiple p53 target genes are downregulated when c-Myc is present, including p21WAF1, MDM2, PERP, NOXA, GADD45, DDB2, PIR121 and p53R2. Also, a number of genes that are upregulated by c-Myc in cells expressing wild-type conformation p53 encode chaperones related to cell death protection as HSP105, HSP90 and HSP27. Both downregulation of p53 target genes and upregulation of chaperones could explain the inhibition of apoptosis observed in K562 cells with ectopic c-Myc. Myc-mediated impairment of p53 transactivation was not restricted to K562 cells, but it was reproduced in a panel of human cancer cell lines derived from different tissues. Our data suggest that elevated levels of Myc counteract p53 activity in human tumor cells that lack ARF. This mechanism could contribute to explain the c-Myc deregulation frequently found in cancer.

El rol del sexo en la estructura de la población de nematodes en una especie de anfibio del Monte de Argentina / The role of sex in the structure of the nematode population in an amphibian species from Monte de Argentina

Diversos estudios comparativos han demostrado que los hospedadores machos no sólo podrían albergar más parásitos que las hembras, sino también tener un rol en la estructura de la población de nematodes. Debido a esto, debatimos la función que tiene el sexo en el parasitismo en una población de anfibios en un sector del monte. Analizamos el contenido gastrointestinal en busca de endoparásitos de 43 ejemplares de Pleurodema nebulosum (Burmeister, 1861), 38 adultos (26 machos y 12 hembras) y 5 juveniles. Nuestros resultados indicaron que únicamente machos se encontraban parasitados asociado con una curva correspondiente a un modelo parasitismo/ rango - edad tipo III. Aplectana nebulosa Piñeiro-Gómez, González & Sanabria, 2017 (Nematoda: Cosmocercidae) presenta un patrón de distribución agregado ajustado a un modelo Poisson. Pleurodema nebulosum (Anura: Leptodactylidae) es oportunista para reproducirse en periodos de lluvia, debido a esto nosotros proponemos como hipótesis que el momento de infección por nematodes probablemente ocurra durante estos cortos periodos en lagunas temporales formadas. El parasitismo en machos podría estar relacionado a factores hormonales debido al periodo reproductivo. Por lo tanto el sexo sería un factor importante en la estructuración de las poblaciones parásitas de esta especie de anfibio.(AU)

The role of sex in the structure of the nematode population in an amphibian species from Monte de Argentina. Several comparative studies demonstrated that male host could have more parasites than female, in a way that host sex could play a role in the structure of the nematode parasite populations. Here we discussed the role of sex of parasitism in an amphibian population in a sector of the Monte. We analyzed the gastrointestinal content for endoparasites of 43 Pleurodema nebulosum (Burmeister, 1861) specimens, 38 adults (26 males and 12 females) and 5 juveniles. Our results indicated that only males were parasitized associated with a curve corresponding to a type III model. Aplectana nebulosa Piñeiro-Gómez, González & Sanabria, 2017 (Nematoda: Cosmocercidae) presents an aggregate distribution pattern adjusted to a Poisson model. Pleurodema nebulosum (Anura: Leptodactylidae) is opportunistic to reproduce in periods of rain, because of this we propose the hypothesis that the moment of infection by nematodes probably occurs during these short periods in temporary lagoons formed. Parasitism in males may be related to hormonal factors due to the reproductive period. Therefore, sex would be an important factor that structures parasitism in this species of amphibian.(AU)

El rol del sexo en la estructura de la población de nematodes en una especie de anfibio del Monte de Argentina / The role of sex in the structure of the nematode population in an amphibian species from Monte de Argentina

Diversos estudios comparativos han demostrado que los hospedadores machos no sólo podrían albergar más parásitos que las hembras, sino también tener un rol en la estructura de la población de nematodes. Debido a esto, debatimos la función que tiene el sexo en el parasitismo en una población de anfibios en un sector del monte. Analizamos el contenido gastrointestinal en busca de endoparásitos de 43 ejemplares de Pleurodema nebulosum (Burmeister, 1861), 38 adultos (26 machos y 12 hembras) y 5 juveniles. Nuestros resultados indicaron que únicamente machos se encontraban parasitados asociado con una curva correspondiente a un modelo parasitismo/ rango - edad tipo III. Aplectana nebulosa Piñeiro-Gómez, González & Sanabria, 2017 (Nematoda: Cosmocercidae) presenta un patrón de distribución agregado ajustado a un modelo Poisson. Pleurodema nebulosum (Anura: Leptodactylidae) es oportunista para reproducirse en periodos de lluvia, debido a esto nosotros proponemos como hipótesis que el momento de infección por nematodes probablemente ocurra durante estos cortos periodos en lagunas temporales formadas. El parasitismo en machos podría estar relacionado a factores hormonales debido al periodo reproductivo. Por lo tanto el sexo sería un factor importante en la estructuración de las poblaciones parásitas de esta especie de anfibio.

The role of sex in the structure of the nematode population in an amphibian species from Monte de Argentina. Several comparative studies demonstrated that male host could have more parasites than female, in a way that host sex could play a role in the structure of the nematode parasite populations. Here we discussed the role of sex of parasitism in an amphibian population in a sector of the Monte. We analyzed the gastrointestinal content for endoparasites of 43 Pleurodema nebulosum (Burmeister, 1861) specimens, 38 adults (26 males and 12 females) and 5 juveniles. Our results indicated that only males were parasitized associated with a curve corresponding to a type III model. Aplectana nebulosa Piñeiro-Gómez, González & Sanabria, 2017 (Nematoda: Cosmocercidae) presents an aggregate distribution pattern adjusted to a Poisson model. Pleurodema nebulosum (Anura: Leptodactylidae) is opportunistic to reproduce in periods of rain, because of this we propose the hypothesis that the moment of infection by nematodes probably occurs during these short periods in temporary lagoons formed. Parasitism in males may be related to hormonal factors due to the reproductive period. Therefore, sex would be an important factor that structures parasitism in this species of amphibian.

El rol del sexo en la estructura de la población de nematodes en una especie de anfibio del Monte de Argentina

RESUMEN Diversos estudios comparativos han demostrado que los hospedadores machos no sólo podrían albergar más parásitos que las hembras, sino también tener un rol en la estructura de la población de nematodes. Debido a esto, debatimos la función que tiene el sexo en el parasitismo en una población de anfibios en un sector del monte. Analizamos el contenido gastrointestinal en busca de endoparásitos de 43 ejemplares de Pleurodema nebulosum (Burmeister, 1861), 38 adultos (26 machos y 12 hembras) y 5 juveniles. Nuestros resultados indicaron que únicamente machos se encontraban parasitados asociado con una curva correspondiente a un modelo parasitismo/ rango - edad tipo III. Aplectana nebulosa Piñeiro-Gómez, González & Sanabria, 2017 (Nematoda: Cosmocercidae) presenta un patrón de distribución agregado ajustado a un modelo Poisson. Pleurodema nebulosum (Anura: Leptodactylidae) es oportunista para reproducirse en periodos de lluvia, debido a esto nosotros proponemos como hipótesis que el momento de infección por nematodes probablemente ocurra durante estos cortos periodos en lagunas temporales formadas. El parasitismo en machos podría estar relacionado a factores hormonales debido al periodo reproductivo. Por lo tanto el sexo sería un factor importante en la estructuración de las poblaciones parásitas de esta especie de anfibio.

ABSTRACT The role of sex in the structure of the nematode population in an amphibian species from Monte de Argentina. Several comparative studies demonstrated that male host could have more parasites than female, in a way that host sex could play a role in the structure of the nematode parasite populations. Here we discussed the role of sex of parasitism in an amphibian population in a sector of the Monte. We analyzed the gastrointestinal content for endoparasites of 43 Pleurodema nebulosum (Burmeister, 1861) specimens, 38 adults (26 males and 12 females) and 5 juveniles. Our results indicated that only males were parasitized associated with a curve corresponding to a type III model. Aplectana nebulosa Piñeiro-Gómez, González & Sanabria, 2017 (Nematoda: Cosmocercidae) presents an aggregate distribution pattern adjusted to a Poisson model. Pleurodema nebulosum (Anura: Leptodactylidae) is opportunistic to reproduce in periods of rain, because of this we propose the hypothesis that the moment of infection by nematodes probably occurs during these short periods in temporary lagoons formed. Parasitism in males may be related to hormonal factors due to the reproductive period. Therefore, sex would be an important factor that structures parasitism in this species of amphibian.

Amifostine impairs p53-mediated apoptosis of human myeloid leukemia cells.

Amifostine is used as a cytoprotective agent in cancer treatments. Amifostine protects from apoptosis in some models and has been used as hematopoiesis stimulator in myeloid malignancies. As the apoptosis induced by many antitumoral agents is mediated by p53, we studied the effect of amifostine on p53-mediated apoptosis. We used human myeloid leukemia K562 and NB4 cells expressing the temperature-conditional p53-Val(135) mutant. Both cell lines undergo apoptosis at 32 degrees C due to the presence of p53 in wild-type conformation. We found that amifostine dramatically reduced apoptosis by p53 in both cell lines, as assessed by cell morphology, annexin V binding, fraction of sub-G(1) cells, and DNA laddering. To explore the mechanism responsible for this apoptosis protection, we tested the effect of amifostine on p53 transcriptional activity. We found that amifostine reduced p53-mediated transactivation of target promoters in NB4 and K562. Macroarray analysis confirmed that several p53 target genes as p21(Waf1), mdm2, gadd45, pig8, and pig3 were down-regulated at the mRNA level by amifostine in NB4 and K562. Also, c-myc was up-regulated by amifostine in K562 in the presence of p53, consistently with the impairment of p53-mediated apoptosis exerted by c-Myc in these cells. We conclude that amifostine impairs p53-dependent apoptosis of myeloid leukemia cells by reducing the activation of apoptosis-related genes. Our results open the possibility that amifostine could reduce the effectiveness of antitumoral treatments when it is dependent on active p53.

Uso y selección de microhábitat en un ensamble de anuros del Chaco Serrano de Argentina / Microhabitat use and selection by an anuran assemblage from the Chaco Serrano of Argentina

Introducción: El estudio de las estrategias de uso y partición del recurso espacial resulta importante para entender los mecanismos de coexistencia de especies de anfibios simpátricas, más aún cuando existen variaciones temporales en la disponibilidad de hábitats. Objetivo: Conocer los patrones de uso de microhábitat, sus variaciones estacionales y la posible influencia de la filogenia en un ensamble de anuros del Chaco Serrano de Argentina. Métodos: Los muestreos se realizaron en el área protegida Parque Natural Valle Fértil, Departamento Valle Fértil, San Juan, entre el 2012 y 2017. En campo, se registró el microhábitat donde se encontró cada ejemplar y se midieron variables del sitio. Además, se determinó la disponibilidad de microhábitats. Los datos se analizaron mediante el índice de selectividad de Manly. Para evaluar variaciones temporales en el uso de microhábitats se utilizaron modelos lineales generalizados (GLM). Resultados: Las especies evaluadas fueron: Rhinella arenarum arenarum, Leptodactylus latrans, Pleurodema tucumanum y Odontophrynus occidentalis. Todas las especies mostraron diferencias en las frecuencias de uso: R. a. arenarum mostró preferencias hacia los sitios rocosos y acuáticos, P. tucumanum exhibió preferencias hacia los sitios con suelo desnudo y rocas, L. latrans y O. occidentalis presentaron mayores preferencias hacia los sitios rocosos y acuáticos. Todas las especies excepto Odontophrynus exhibieron variaciones estacionales en la selección y uso de los microhábitats. Odontophrynus occidentalis presentó diferencias en las proporciones de uso entre microhábitats. Conclusiones: Este estudio muestra la plasticidad en el uso de microhábitats como un determinante importante en la distribución espacial de anuros, sin restricciones aparentes impuestas por la competencia, el espacio ni la filogenia. Cuando la actividad de las especies es coincidente, el recurso espacial puede distribuirse de manera que se reduzca el solapamiento entre especies.

Introduction: Research on spatial resource usage and partition strategies is important to understand the mechanisms of coexistence in sympatric amphibian species, even more when there are temporal variations in habitat availability. Objective: To learn about the patterns of microhabitat use, its seasonal variations and the possible influence of phylogeny on an anuran assembly of the Chaco Serrano in Argentina. Methods: Samplings were carried out in the Valle Fértil Natural Park protected area, Valle Fértil Department, San Juan, between 2012 and 2017. In the field, we recorded the microhabitat where each specimen was found, and we also measured site variables. In addition, microhabitats availability was determined. Data were analyzed using Manly's selectivity index. Generalized linear models (GLM) were used to assess temporal variations in microhabitat use. Results: The species evaluated were: Rhinella arenarum arenarum, Leptodactylus latrans, Pleurodema tucumanum and Odontophrynus occidentalis. All species showed differences in usage frequencies: R. a. arenarum showed preferences for rocky and aquatic sites, P. tucumanum showed preferences towards bare soil and rocky sites, L. latrans and O. occidentalis showed greater preferences for rocky and aquatic sites. All species but Odontophrynus exhibited seasonal variations in microhabitat selection and usage. Odontophrynusoccidentalis showed differences in usage proportions among microhabitats. Conclusions: This study shows plasticity in microhabitat usage as an important determinant of anuran spatial distribution, without apparent restrictions imposed by space competition or phylogeny. When species activity is coincident, the space resource may be distributed in a way that species overlap is reduced.

MGMT Expression Predicts PARP-Mediated Resistance to Temozolomide.

Melanoma and other solid cancers are frequently resistant to chemotherapies based on DNA alkylating agents such as dacarbazine and temozolomide. As a consequence, clinical responses are generally poor. Such resistance is partly due to the ability of cancer cells to use a variety of DNA repair enzymes to maintain cell viability. Particularly, the expression of MGMT has been linked to temozolomide resistance, but cotargeting MGMT has proven difficult due to dose-limiting toxicities. Here, we show that the MGMT-mediated resistance of cancer cells is profoundly dependent on the DNA repair enzyme PARP. Both in vitro and in vivo, we observe that MGMT-positive cancer cells strongly respond to the combination of temozolomide and PARP inhibitors (PARPi), whereas MGMT-deficient cells do not. In melanoma cells, temozolomide induced an antiproliferative senescent response, which was greatly enhanced by PARPi in MGMT-positive cells. In summary, we provide compelling evidence to suggest that the stratification of patients with cancer upon the MGMT status would enhance the success of combination treatments using temozolomide and PARPi.

Assessment of the predatory capacity on mosquito larvae of Jenynsia multidentata (Anablepidae) in presence of vegetation under laboratory conditions / Evaluación de la capacidad depredadora de Jenynsia multidentata (Anablepidae) sobre larvas de mosquitos en presencia de vegetación en condiciones de laboratorio

Los peces larvívoros han sido estudiados como posibles agentes de control biológico de larvas y pupas de mosquitos a través de sus interacciones tróficas. El uso de peces nativos para el control de mosquitos puede tener beneficios tanto para la biodiversidad acuática como para la salud humana. La evaluación del efecto de la vegetación sobre la eficacia depredadora es fundamental para determinar si esta especie puede usarse como un agente de control biológico. Con el objetivo de evaluar a Jenynsia multidentata (Jenyns, 1842) como agente de biocontrol de Culex pipiens Linnaeus, 1758, probamos su capacidad depredadora en presencia o ausencia de vegetación acuática en condiciones de laboratorio. Se llevaron a cabo dos experimentos independientes. El consumo de larvas a una densidad de 60 larvas (6 larvas / l) se redujo significativamente con el aumento de la vegetación. Por otro lado, cuando la densidad larval fue de 120 (12 larvas / l), la capacidad depredadora de J. multidentata no varía en la presencia o ausencia de vegetación. Este resultado indicó que el efecto de la vegetación en el consumo podría estar relacionado con la densidad de presas, ya que a mayor densidad de presas se podría incrementar la probabilidad de encuentro entre depredador y presa. Jenynsia multidentata es un buen consumidor en presencia de vegetación y podría ser usado como un potencial agente de control biológico de larvas de mosquitos en ambientes naturales con características similares a las probadas en estos experimentos.(AU)

Larvivorous fish have been studied as potential biocontrol agents of mosquito larvae and pupae through their trophic interactions. The use of native sh for mosquito control may have benets for both aquatic biodiversity and human health. Evaluating the effect of vegetation on the predatory efficacy is fundamental to determine if this species can be used as a biocontrol agent. With the aim of evaluating Jenynsia multidentata (Jenyns, 1842) as a biocontrol agent of Culex pipiens Linnaeus, 1758, we tested its predatory capacity in the presence or absence of aquatic vegetation under laboratory conditions. Two independent experiments were conducted. Larval consumption at a density of 60 larvae (6 larvae/l) was significantly reduced with the vegetation increased. On the other hand, when the larval density was 120 (12 larvae/l), the predatory capacity of J. multidentata did not vary in the presence or absence of vegetation. This result indicated that vegetation effect on consumption could be related to prey density, since at the higher density of prey the probability of predator-prey encounter might be increased. Jenynsia multidentata is a good consumer in presence of vegetation and could be used as a potential biocontrol agent of mosquito larvae in natural environments with similar characteristics to the ones tested in these experiments.(AU)