Coculture of Astroglial and Vascular Endothelial Cells as Apposing Layers Enhances the Transcellular Transport of Hypoxanthine

Abstract: In brain, astrocytes and endothelial cells are a major site of adenosine degradation. These two cell types, found in close apposition, constitute the wall of the brain's capillaries and serve as a site of hypoxanthine production and degradation. Both cell types possess the hypoxanthine salvage pathway and can incorporate hypoxanthine into nucleotides. This suggests that the endothelial-astrocyte anatomical complex might play an important role in the brain's purine homeostasis. To test this hypothesis, cocultures of monolayers of vascular endothelial cells and astrocytes were grown over a porous membrane, in close apposition to one another, and studies on hypoxanthine transport and metabolism to uric acid were performed. The flux of hypoxanthine across the cell layers was simultaneously determined and compared with the flux of sucrose, as a probe of passive diffusion. Our results show that in endothelial, glial, and endothelial-glial cell layers the hypoxanthine flux was greater than that of sucrose, and that the flux of hypoxanthine, but not of sucrose, was inhibited by adenine or by lowering the temperature. These results suggest that hypoxanthine moves across endothelial, glial, and endothelial-glial cell layers by a transport process. Furthermore, we found that hypoxanthine transport is enhanced when glial and endothelial cells are cocultured compared with that in glial or endothelial monolayers. In addition the coculture also resulted in a depression of xanthine oxidase activity.     

Impact of Non-Native Birds on Native Ecosystems: A Global Analysis

Introduction and naturalization of non-native species is one of the most important threats to global biodiversity. Birds have been widely introduced worldwide, but their impacts on populations, communities, and ecosystems have not received as much attention as those of other groups. This work is a global synthesis of the impact of nonnative birds on native ecosystems to determine (1) what groups, impacts, and locations have been best studied; (2) which taxonomic groups and which impacts have greatest effects on ecosystems, (3) how important are bird impacts at the community and ecosystem levels, and (4) what are the known benefits of nonnative birds to natural ecosystems. We conducted an extensive literature search that yielded 148 articles covering 39 species belonging to 18 families -18% of all known naturalized species. Studies were classified according to where they were conducted: Africa, Asia, Australasia, Europe, North America, South America, Islands of the Indian, of the Pacific, and of the Atlantic Ocean. Seven types of impact on native ecosystems were evaluated: competition, disease transmission, chemical, physical, or structural impact on ecosystem, grazing/ herbivory/ browsing, hybridization, predation, and interaction with other non-native species. Hybridization and disease transmission were the most important impacts, affecting the population and community levels. Ecosystem-level impacts, such as structural and chemical impacts were detected. Seven species were found to have positive impacts aside from negative ones. We provide suggestions for future studies focused on mechanisms of impact, regions, and understudied taxonomic groups.     

Medicinal plants of the Argentine Yungas plants of the Las Yungas biosphere reserve, Northwest of Argentina, used in health care

We have compared the species richness of medicinal plants and the differential patterns of use amongst settlements in the Andean communities of Northwest Argentina which have differing levels of isolation. About 259 ethnoespecies, belonging to 74 plant families, were included, representing between 70 and 80% of the total estimate. The results indicate that Coronopus didymus is the most relevant and important species. The method of use of medicinal plants and the ailments treated by rural doctors compared to those of the layperson is different. Native and exotic plants are used differently according to the body system treated. There are some relationships between internal and external use and body systems and recipes. The greater medicinal species richness found in the less isolated locations is due to external enriching cultural influences.     

Reproductive biology of South American Bothriochloa (Poaceae: Andropogoneae)

The reproductive biology of 13 South American taxa of Bothriochloa was studied. All surveyed species reproduce sexually and are self-compatible. Several elements also point to self-pollination as their main breeding system: (i) bud pollination that occurs in most species enhancing cleistogamy, (ii) presence of pits in the glumes that impede the opening of flowers and (iii) reduction in the number of stamens, a trend associated with outbreeding.     

Similar and opposite effects of dibutyryl cyclic AMP and insulin on glucose metabolism in adipose tissue

The effects of N⁶-2′-O-dibutyryl cyclic AMP on glucose metabolism and lipolysis in fragments of rat epididymal adipose tissue were studied. Measurements were made of glucose uptake, conversion of glucose carbon to CO₂ and tissue fatty acids and glyceride-glycerol, lactate production, and glycerol release. Low concentrations of dibutyryl cyclic AMP (0.1–0.5 mM) increased all parameters of glucose metabolism and inhibited glycerol release in tissue from both normally fed and fasted rats. Higher concentrations of dibutyryl cyclic AMP (3–5 mM) diminished glucose utilization and greatly accelerated lipolysis. Insulin, 50 μunits/ml, accelerated glucose metabolism in the presence of either low or high concentrations of dibutyryl cyclic AMP though the effect of insulin was greatly reduced by 3 mM dibutyryl cyclic AMP. Tissue exposed to concentrations of dibutyryl cyclic AMP which inhibited glucose metabolism (5 mM), then rinsed and reincubated without dibutyryl cyclic AMP, displayed increased glucose utilization. The results of these experiments emphasize the need for caution in interpretation of the effects of dibutyryl cyclic AMP on adipose tissue metabolism and the need for further research to elucidate the role of cyclic AMP in the regulation of glucose metabolism.     

The pre-Columbian dog from Arica,Chile

Burials and mummies of dogs from the Arica, Chile, area are described. It is concluded that these dogs were brought to this area 2500 years ago by shepherds from the highlands and are still present, relatively unchanged.     

AVPR1b variation and the emergence of adaptive phenotypes in Platyrrhini primates

Platyrrhini (New World monkeys, NWm) are a group of primates characterized by behavioral and reproductive traits that are otherwise uncommon among primates, including social monogamy, direct paternal care, and twin births. As a consequence, the study of Platyrrhine primates is an invaluable tool for the discovery of the genetic repertoire underlying these taxon‐specific traits. Recently, high conservation of vasopressin (AVP) sequence, in contrast with high variability of oxytocin (OXT), has been described in NWm. AVP and OXT functions are possible due to interaction with their receptors: AVPR1a, AVPR1b, AVPR2, and OXTR; and the variability in this system is associated with the traits mentioned above. Understanding the variability in the receptors is thus fundamental to understand the function and evolution of the system as a whole. Here we describe the variability of AVPR1b coding region in 20 NWm species, which is well‐known to influence behavioral traits such as aggression, anxiety, and stress control in placental mammals. Our results indicate that 4% of AVPR1b sites may be under positive selection and a significant number of sites under relaxed selective constraint. Considering the known role of AVPR1b, we suggest that some of the changes described here for the Platyrrhini may be a part of the genetic repertoire connected with the complex network of neuroendocrine mechanisms of AVP–OXT system in the modulation of the HPA axis. Thus, these changes may have promoted the emergence of social behaviors such as direct paternal care in socially monogamous species that are also characterized by small body size and twin births.