Land Use Influences Niche Size and the Assimilation of Resources by Benthic Macroinvertebrates in Tropical Headwater Streams

It is well recognized that assemblage structure of stream macroinvertebrates changes with alterations in catchment or local land use. Our objective was to understand how the trophic ecology of benthic macroinvertebrate assemblages responds to land use changes in tropical streams. We used the isotope methodology to assess how energy flow and trophic relations among macroinvertebrates were affected in environments affected by different land uses (natural cover, pasture, sugar cane plantation). Macroinvertebrates were sampled and categorized into functional feeding groups, and available trophic resources were sampled and evaluated for the isotopic composition of ¹³C and ¹⁵N along streams located in the Cerrado (neotropical savanna). Streams altered by pasture or sugar cane had wider and more overlapped trophic niches, which corresponded to more generalist feeding habits. In contrast, trophic groups in streams with native vegetation had narrower trophic niches with smaller overlaps, suggesting greater specialization. Pasture sites had greater ranges of resources exploited, indicating higher trophic diversity than sites with natural cover and sugar cane plantation. We conclude that agricultural land uses appears to alter the food base and shift macroinvertebrate assemblages towards more generalist feeding behaviors and greater overlap of the trophic niches.     

Multiple Exposures to Ascaris suum Induce Tissue Injury and Mixed Th2/Th17 Immune Response in Mice

Ascaris spp. infection affects 800 million people worldwide, and half of the world population is currently at risk of infection. Recurrent reinfection in humans is mostly due to the simplicity of the parasite life cycle, but the impact of multiple exposures to the biology of the infection and the consequences to the host’s homeostasis are poorly understood. In this context, single and multiple exposures in mice were performed in order to characterize the parasitological, histopathological, tissue functional and immunological aspects of experimental larval ascariasis. The most important findings revealed that reinfected mice presented a significant reduction of parasite burden in the lung and an increase in the cellularity in the bronchoalveolar lavage (BAL) associated with a robust granulocytic pulmonary inflammation, leading to a severe impairment of respiratory function. Moreover, the multiple exposures to Ascaris elicited an increased number of circulating inflammatory cells as well as production of higher levels of systemic cytokines, mainly IL-4, IL-5, IL-6, IL-10, IL-17A and TNF-α when compared to single-infected animals. Taken together, our results suggest the intense pulmonary inflammation associated with a polarized systemic Th2/Th17 immune response are crucial to control larval migration after multiple exposures to Ascaris.     

Unmasking of nerve growth factor membrane-specific binding sites in synchronized murine C 1300 neuroblastoma cells

The resistance to actinomycin D (AD) of a clone of SV40 virus-transformed hamster cells (TSV5 C12 A^R) was investigated. This line was found to be much less permeable to the antibiotic. Penetration of proflavine and puromycin is also greatly reduced without any prior selection for these drugs. The AD that enters the cells is capable of inhibiting RNA synthesis. Thus the resistance of these cells to AD seems to be due only to the decreased permeability of the drugs possibly resulting from an alteration of the cell membrane.     

Oxytocin acts as an antidepressant in two animal models of depression

In the behavioral despair test in mice, oxytocin, i.p. injected 60 min before testing, significantly reduced the duration of immobility at doses of 0.250-1.0 mg/Kg; the effect being similar to that of imipramine (7.5-30 mg/Kg i.p.). A more powerful effect was obtained with a 10-day treatment schedule. In the learned helplessness test, oxytocin (0.500 mg/Kg/day i.p. for 8 days) significantly reduced the escape failures and the latency to escape, the effect being even more intense than that of imipramine (20 mg/Kg/day i.p. for 8 days). These results show a new behavioral effect of oxytocin, and further support its role of CNS regulatory peptide.     

Flavonoids from Iryanthera laevis

Trunk wood of Iryanthera laevis Markgr. (Myristicaceae) contains 2′,4′-dihydroxy- 4,6′dimethoxydihydrochalcone, three 2′-hydroxy-4′,5′-methylenedioxyflavans with differently substituted A-rings (7-OH-6,8-diMe; 7-OH-5,8-diMe; 5-OH-7-OMe-6,8-diMe) and 1-(2′-hydroxy-4′-methoxy-5′-methylphenyl)-3(2″-hydroxy-4″,5″-methylenedioxphenyl)- propane, as well as three additional known diarylpropanes.     

The structure of the liver cells during the life cycle of a brook-lamprey (Lampetra zanandreai)

Summary From the cytological point of view the liver of the ammocoetes is comparable to the liver of other vertebrates. In the species of lamprey studied (L.zanandreai), metamorphosis marks the beginning of a period of fasting and sexual maturation, during which atrophy of the digestive system occurs. During this period the liver undergoes a complete transformation, that is particularly evident at the ultrastructural level, and results in bile stasis. Bile pigments, and together with them a considerable quantity of ferritin, become concentrated within large dense bodies. Despite their enormous increase in volume and morphological variability, these bodies retain some structural and cytochemical characteristics, i.e., the affinity of their limiting membrane for phosphotungstic acid and the presence of acid phosphatase activity, that justify their identification as transformed lysosomes.