Comparing bird assemblages in large and small fragments of the Atlantic Forest hotspots

The Atlantic Forest (AF) is one of the five most threatened and megadiverse world hotspots. It is arguably the most devastated and highly threatened ecosystem on the planet. The vast scope of habitat loss and extreme fragmentation in the AF hotspots has left intact very few extensive and continuous forested fragments. We compared bird assemblages between small (<100 ha) and large (>6,000 ha) forest remnants, in one of the largest AF remnants in Argentina. We performed 84 point-counts of birds in four large fragments (LF) and 67 points in 25 small fragments (SF). We recorded 4,527 bird individuals belonging to 173 species; 2,632 belonging to 153 species in LF and 1,897 in 124 species in SF. Small fragments suffered a significant loss of bird richness, mainly forest dependent species, but the birds abundance did not decrease, due to an increase in abundance of forest independent and semi-dependent bird species (edge and non forest species) that benefit from forest fragmentation. The bird guilds of frugivores, undestory, terrestrial and midstory insectivores, nectarivores and raptors, and the endemic species of AF were area sensitive, decreasing significantly in richness and abundance in the SF. Terrestrial granivores were the only guild positively affected by forest fragmentation, containing mainly edge species, which forage in open areas or borders including crops. Our first observations on fragmentation effects on bird assemblages in the southernmost Argentinean Atlantic Forests did not validate the hypothesis on pre-adaptation to human disturbances in the bird communities of AF. On the contrary, we observed that forest dependent, endemic and several sensitive bird guilds were strongly affected by fragmentation, putting in evidence the vulnerability to the fragmentation process and the necessity to conserve large remnants to avoid reduction of the high biodiversity of AF birds.     

Alterations in osteoclast morphology following osteoprotegerin administration in the magnesium-deficient mouse

In the present study, we used osteoprotegerin (OPG), which blocks osteoclastogenesis, to correct and thus explain the hypercalcemia that is seen during dietary Mg deficiency in the mouse. Control and Mg-deficient mice received injections for 12 days of either OPG or vehicle only. Serum Ca was similar in Mg-deficient mice treated with OPG and in control mice receiving OPG (9.2±0.3 mg/dl vs. 9.2±0.5). Both groups had significantly higher serum Ca than controls or Mg-deficient animals receiving vehicle alone. Surprisingly, Mg-depleted mice that received OPG in doses that inhibit osteoclastic bone resorption remained hypercalcemic. Because mature osteoclasts still present in the marrow might be hyperactive, we examined osteoclast morphology at the light microscopic and ultrastructural level. Light microscopic examination of trabecular bone showed few osteoclasts in OPG-treated mice. Ultrastructural examination revealed that osteoclasts in OPG-treated mice have decreased contact with the endosteal bone surface and absence of a ruffled border. Because the morphology of the existing pool of mature osteoclasts did not enhance resorption, another mechanism, such as increased intestinal absorption of Ca in Mg-deficient mice, likely contributes to the hypercalcemia observed during Mg deficiency.     

Avian predation on a parasitic fly of cervids during winter: can host‐related cues increase the predation risk?

The deer ked (Lipoptena cervi) is an ectoparasitic fly on cervids that has expanded its distribution rapidly in Northern Europe. However, the regulating biotic factors such as predation remain unknown. The host‐independent pupal stage of the fly lasts for several months. Blackish pupae are visible against snow, especially on the bedding sites of hosts, and are thus exposed to predators. To evaluate the role of predation on the invasion dynamics and evolution of L. cervi, we monitored pupal predation on artificial bedding sites in three geographical areas in Finland during winter. We explored: (1) possible predators; (2) magnitude of predation; and (3) whether predation risk is affected by host‐derived cues. We demonstrate that pupae are predated by a number of tit species. Any reddish brown snow discoloration on bedding sites, indicating heavy infestation of the host, serves as an exploitable cue for avian predators, thereby increasing the risk of pupal predation. The ability of tits to use this host‐derived cue seems to be dependent on the prevalence of L. cervi and the period of invasion history, which suggests that it may be a learned behavioural response. Predation by tits may potentially affect the L. cervi population dynamics locally. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 106 , 275–286.     

Induction of eIF-4E phosphorylation by the addition of L-pyrroline-5-carboxylic acid to rabbit reticulocyte lysate

Addition of L-pyrroline-5-carboxylic acid to reticulocyte lysates inhibits protein synthesis and induced phosphoproteins of 25 and 14 kDa. The 25 kDa phosphoprotein had the same Mr and pI as phosphorylated eIF-4E. Incubation of lysates with L-pyrroline-5-carboxylic acid did not alter the crosslinking of eIF-4E to reovirus mRNA caps. These results suggest that modifications of the translational apparatus other than eIF-4E phosphorylation may mediate the inhibitory effect seen with L-pyrroline-5-carboxylic acid and/or that phosphorylation of eIF-4E may effect functions subsequent to its interaction with the mRNA cap such as protein-protein interactions with other cap-specific translation factors.     

Structure of cytochrome c oxidase: a comparison of the bacterial and mitochondrial enzymes

It has been almost 5 years since the first structures of cytochrome c oxidase, from Paracoccus denitrificans and bovine heart mitochondria, were revealed. Since then many different proton pumping mechanisms have been proposed for the enzyme; however, no definitive conclusion has been achieved. In this article, we revisit the original structures of bacterial and mitochondrial oxidases and try to clarify similarities as well as differences between the two structures.     

Induction of pulmonary matrilysin expression by combustion and ambient air particles

The molecular mechanism(s) by which chemically complex air pollution particles mediate their adverse health effects is not known. We have examined the ability of combustion and ambient air particles to induce pulmonary matrilysin expression due to the well-documented role of matrix metalloproteinases in tissue injury and repair responses. Rats were exposed to saline, residual oil fly ash (2.5 mg/rat), or ambient air particles (2.5 mg/rat) via intratracheal instillation and examined 3-72 h after exposure. Saline-exposed animals had low levels of matrilysin mRNA, whereas the animals exposed to either complex particle showed an early induction of pulmonary matrilysin gene expression as well as of the 19-kDa activated form of matrilysin. Immunocytochemistry and in situ hybridization analyses identified the alveolar macrophages and monocytes as primary sources of air pollution particle-induced matrilysin expression. Matrilysin gene induction and protein activation by combustion and ambient air particles correlated with the early histopathological changes produced by these particles. These results demonstrate the ability of combustion and ambient air particles to induce pulmonary matrilysin expression and suggest a role for this matrix metalloproteinase in the initiation of lung injury produced by these particles.     

The physiology and ecological implications of efficient growth

The natural habitats of microbes are typically spatially structured with limited resources, so opportunities for unconstrained, balanced growth are rare. In these habitats, selection should favor microbes that are able to use resources most efficiently, that is, microbes that produce the most progeny per unit of resource consumed. On the basis of this assertion, we propose that selection for efficiency is a primary driver of the composition of microbial communities. In this article, we review how the quality and quantity of resources influence the efficiency of heterotrophic growth. A conceptual model proposing innate differences in growth efficiency between oligotrophic and copiotrophic microbes is also provided. We conclude that elucidation of the mechanisms underlying efficient growth will enhance our understanding of the selective pressures shaping microbes and will improve our capacity to manage microbial communities effectively.