Bats associated with inactive mines in the Great Basin

We surveyed bats using echolocation calls near inactive mines in the western Great Basin from 2003 to 2007. We identified 14 species of bats during our surveys, with Myotis lucifugus and Lasionycteris noctivagans found at 9 sites and Myotis evotis and Tadarida brasiliensis at 7 sites; all other species were found at less than one-half of the sites. Euderma maculatum, a state-protected species in Nevada, was recorded at 2 sites. Our work provides information that will be useful in managing bat habitat, especially with regard to mining activities.     

Endothelial and perivascular cells maintain haematopoietic stem cells

Several cell types have been proposed to create niches for haematopoietic stem cells (HSCs). However, the expression patterns of HSC maintenance factors have not been systematically studied and no such factor has been conditionally deleted from any candidate niche cell. Thus, the cellular sources of these factors are undetermined. Stem cell factor (SCF; also known as KITL) is a key niche component that maintains HSCs. Here, using Scf(gfp) knock-in mice, we found that Scf was primarily expressed by perivascular cells throughout the bone marrow. HSC frequency and function were not affected when Scf was conditionally deleted from haematopoietic cells, osteoblasts, nestin-cre- or nestin-creER-expressing cells. However, HSCs were depleted from bone marrow when Scf was deleted from endothelial cells or leptin receptor (Lepr)-expressing perivascular stromal cells. Most HSCs were lost when Scf was deleted from both endothelial and Lepr-expressing perivascular cells. Thus, HSCs reside in a perivascular niche in which multiple cell types express factors that promote HSC maintenance.     

Oligodendroglia metabolically support axons and contribute to neurodegeneration

Oligodendroglia support axon survival and function through mechanisms independent of myelination, and their dysfunction leads to axon degeneration in several diseases. The cause of this degeneration has not been determined, but lack of energy metabolites such as glucose or lactate has been proposed. Lactate is transported exclusively by monocarboxylate transporters, and changes to these transporters alter lactate production and use. Here we show that the most abundant lactate transporter in the central nervous system, monocarboxylate transporter 1 (MCT1, also known as SLC16A1), is highly enriched within oligodendroglia and that disruption of this transporter produces axon damage and neuron loss in animal and cell culture models. In addition, this same transporter is reduced in patients with, and in mouse models of, amyotrophic lateral sclerosis, suggesting a role for oligodendroglial MCT1 in pathogenesis. The role of oligodendroglia in axon function and neuron survival has been elusive; this study defines a new fundamental mechanism by which oligodendroglia support neurons and axons.     

The primate amygdala represents the positive and negative value of visual stimuli during learning

Visual stimuli can acquire positive or negative value through their association with rewards and punishments, a process called reinforcement learning. Although we now know a great deal about how the brain analyses visual information, we know little about how visual representations become linked with values. To study this process, we turned to the amygdala, a brain structure implicated in reinforcement learning. We recorded the activity of individual amygdala neurons in monkeys while abstract images acquired either positive or negative value through conditioning. After monkeys had learned the initial associations, we reversed image value assignments. We examined neural responses in relation to these reversals in order to estimate the relative contribution to neural activity of the sensory properties of images and their conditioned values. Here we show that changes in the values of images modulate neural activity, and that this modulation occurs rapidly enough to account for, and correlates with, monkeys' learning. Furthermore, distinct populations of neurons encode the positive and negative values of visual stimuli. Behavioural and physiological responses to visual stimuli may therefore be based in part on the plastic representation of value provided by the amygdala.     

Impact of localized badger culling on tuberculosis incidence in British cattle

Pathogens that are transmitted between wildlife, livestock and humans present major challenges for the protection of human and animal health, the economic sustainability of agriculture, and the conservation of wildlife. Mycobacterium bovis, the aetiological agent of bovine tuberculosis (TB), is one such pathogen. The incidence of TB in cattle has increased substantially in parts of Great Britain in the past two decades, adversely affecting the livelihoods of cattle farmers and potentially increasing the risks of human exposure. The control of bovine TB in Great Britain is complicated by the involvement of wildlife, particularly badgers (Meles meles), which appear to sustain endemic infection and can transmit TB to cattle. Between 1975 and 1997 over 20,000 badgers were culled as part of British TB control policy, generating conflict between conservation and farming interest groups. Here we present results from a large-scale field trial that indicate that localized badger culling not only fails to control but also seems to increase TB incidence in cattle.     

Fusion of bone-marrow-derived cells with Purkinje neurons, cardiomyocytes and hepatocytes

Recent studies have suggested that bone marrow cells possess a broad differentiation potential, being able to form new liver cells, cardiomyocytes and neurons. Several groups have attributed this apparent plasticity to 'transdifferentiation'. Others, however, have suggested that cell fusion could explain these results. Using a simple method based on Cre/lox recombination to detect cell fusion events, we demonstrate that bone-marrow-derived cells (BMDCs) fuse spontaneously with neural progenitors in vitro. Furthermore, bone marrow transplantation demonstrates that BMDCs fuse in vivo with hepatocytes in liver, Purkinje neurons in the brain and cardiac muscle in the heart, resulting in the formation of multinucleated cells. No evidence of transdifferentiation without fusion was observed in these tissues. These observations provide the first in vivo evidence for cell fusion of BMDCs with neurons and cardiomyocytes, raising the possibility that cell fusion may contribute to the development or maintenance of these key cell types.