Laurel L. Haak

Adenosine: A Neuron-Glial Transmitter Promoting Myelination in the CNS in Response to Action Potentials

Neuronal activity influences myelination of the brain, but the molecular mechanisms involved are largely unknown. Here, we report that oligodendrocyte progenitor cells (OPCs) express functional adenosine receptors, which are activated in response to action potential firing. Adenosine acts as a potent neuron-glial transmitter to inhibit OPC proliferation, stimulate differentiation, and promote the formation of myelin. This neuron-glial signal provides a molecular mechanism for promoting oligodendrocyte development and myelination in response to impulse activity and may help resolve controversy on the opposite effects of impulse activity on myelination in the central and peripheral nervous systems.

RACE, ETHNICITY, AND NIH RESEARCH AWARDS

NIH research project grants from 2000 to 2006 show evidence of racial/ethnic disparities in the probability of receiving an award. We investigated the association between a U.S. National Institutes of Health (NIH) R01 applicant’s self-identified race or ethnicity and the probability of receiving an award by using data from the NIH IMPAC II grant database, the Thomson Reuters Web of Science, and other sources. Although proposals with strong priority scores were equally likely to be funded regardless of race, we find that Asians are 4 percentage points and black or African-American applicants are 13 percentage points less likely to receive NIH investigator-initiated research funding compared with whites. After controlling for the applicant’s educational background, country of origin, training, previous research awards, publication record, and employer characteristics, we find that black applicants remain 10 percentage points less likely than whites to be awarded NIH research funding. Our results suggest some leverage points for policy intervention.

Frequency-dependent regulation of rat hippocampal somato-dendritic excitability by the K+ channel subunit Kv2.1

The voltage‐dependent potassium channel subunit Kv2.1 is widely expressed throughout the mammalian CNS and is clustered primarily on the somata and proximal dendrites, but not axons, of both principal neurones and inhibitory interneurones of the cortex and hippocampus. This expression pattern suggests that Kv2.1‐containing channels may play a role in the regulation of pyramidal neurone excitability. To test this hypothesis and to determine the functional role of Kv2.1‐containing channels, cultured hippocampal slices were incubated with antisense oligonucleotides directed against Kv2.1 mRNA. Western blot analysis demonstrated that Kv2.1 protein content of cultured slices decreased > 90 % following 2 weeks of treatment with antisense oligonucleotides, when compared with either control missense‐treated or untreated cultures. Similarly, Kv2.1 immunostaining was selectively decreased in antisense‐treated cultures. Sustained outward potassium currents, recorded in both whole‐cell and outside‐out patch configurations, demonstrated a selective reduction of amplitude only in antisense‐treated CA1 pyramidal neurones. Under current‐clamp conditions, action potential durations were identical in antisense‐treated, control missense‐treated and untreated slices when initiated by low frequency stimulation (0.2 Hz). In contrast, spike repolarization was progressively prolonged during higher frequencies of stimulation (1 Hz) only in cells from antisense‐treated slices. Similarly, action potentials recorded during electrographic interictal activity in the ‘high [K+]o’ model of epilepsy demonstrated pronounced broadening of their late phase only in cells from antisense‐treated slices. Consistent with the frequency‐dependent spike broadening, calcium imaging experiments from single CA1 pyramidal neurones revealed that high frequency Schaffer collateral stimulation resulted in a prolonged elevation of dendritic [Ca2+]i transients only in antisense‐treated neurones. These studies demonstrate that channels containing Kv2.1 play a role in regulating pyramidal neurone somato‐dendritic excitability primarily during episodes of high frequency synaptic transmission.

Sparks and Puffs in Oligodendrocyte Progenitors: Cross Talk between Ryanodine Receptors and Inositol Trisphosphate Receptors

Investigating how calcium release from the endoplasmic reticulum (ER) is triggered and coordinated is crucial to our understanding of how oligodendrocyte progenitor cells (OPs) develop into myelinating cells. Sparks and puffs represent highly localized Ca2+ release from the ER through ryanodine receptors (RyRs) and inositol trisphosphate receptors (IP3Rs), respectively. To study whether sparks or puffs trigger Ca2+ waves in OPs, we performed rapid high-resolution line scan recordings in fluo-4-loaded OP processes. We found spontaneous and evoked sparks and puffs, and we have identified functional cross talk between IP3Rs and RyRs. Local events evoked using the IP3-linked agonist methacholine (MeCh) showed significantly different morphology compared with events evoked using the caffeine analog 3,7-dimethyl-1-propargylxanthine (DMPX). Pretreatment with MeCh potentiated DMPX-evoked events, whereas inhibition of RyRs potentiated events evoked by low concentrations of MeCh. Furthermore, activation of IP3Rs but not RyRs was critical for Ca2+ wave initiation. Using immunocytochemistry, we show OPs express the specific Ca2+ release channel subtypes RyR3 and IP3R2 in patches along OP processes. RyRs are coexpressed with IP3Rs in some patches, but IP3Rs are also found alone. This differential distribution pattern may underlie the differences in local and global Ca2+ signals mediated by these two receptors. Thus, in OPs, interactions between IP3Rs and RyRs determine the spatial and temporal characteristics of calcium signaling, from microdomains to intracellular waves.

ORCID: a system to uniquely identify researchers

The Open Researcher & Contributor ID (ORCID) registry presents a unique opportunity to solve the problem of author name ambiguity. At its core the value of the ORCID registry is that it crosses disciplines, organizations, and countries, linking ORCID with both existing identifier schemes as well as publications and other research activities. By supporting linkages across multiple datasets – clinical trials, publications, patents, datasets – such a registry becomes a switchboard for researchers and publishers alike in managing the dissemination of research findings. We describe use cases for embedding ORCID identifiers in manuscript submission workflows, prior work searches, manuscript citations, and repository deposition. We make recommendations for storing and displaying ORCID identifiers in publication metadata to include ORCID identifiers, with CrossRef integration as a specific example. Finally, we provide an overview of ORCID membership and integration tools and resources.

Metabotropic Glutamate Receptor Activation Modulates Kainate and Serotonin Calcium Response in Astrocytes

Although metabotropic glutamate receptor (mGluR) modulation has been studied extensively in neurons, it has not been investigated in astrocytes. We studied modulation of glutamate-evoked calcium rises in primary astrocyte cultures using fura-2 ratiometric digital calcium imaging. Calcium plays a key role as a second messenger system in astrocytes, both in regulation of many subcellular processes and in long distance intercellular signaling. Suprachiasmatic nucleus (SCN) and cortical astrocytes showed striking differences in sensitivity to glutamate and to mGluR agonists, even after several weeks in culture. Kainate-evoked intracellular calcium rises were inhibited by concurrent application of the type I and II mGluR agonists quisqualate (10 μm),trans-(±)-1-amino-1,3-cyclopentanedicarboxylate (100–500 μm), and (2S-1′S-2′S)-2-(carboxycyclopropyl)glycine (L-CCG-I) (10 μm). Inhibition mediated by L-CCG-I had long-lasting effects (>45 min) in ∼30% of the SCN astrocytes tested. The inhibition could be mimicked by the L-type calcium channel blocker nimodipine (1 μm) as well as by protein kinase C (PKC) activators phorbol 12,13-dibutyrate (10 μm) and phorbol 12-myristate 13-acetate (500 nm), and blocked by the PKC inactivator (±)-1-(5-isoquinolinesulfonyl)-2-methylpiperazine (200 μm), suggesting a mechanism involving PKC modulation of L-type calcium channels. In contrast, mGluRs modulated serotonin (5HT)-evoked calcium rises through a different mechanism. The type III mGluR agonist l-2-amino-4-phosphonobutyrate consistently inhibited 5HT-evoked calcium rises, whereas in a smaller number of cells quisqualate and L-CCG-I showed both inhibitory and additive effects. Unlike the mGluR-kainate interaction, which required a pretreatment with an mGluR agonist and was insensitive to pertussis toxin (PTx), the mGluR modulation of 5HT actions was rapid and was blocked by PTx. These data suggest that glutamate, acting at several metabotropic receptors expressed by astrocytes, could modulate glial activity evoked by neurotransmitters and thereby influence the ongoing modulation of neurons by astrocytes.

Mitochondria regulate Ca2+ wave initiation and inositol trisphosphate signal transduction in oligodendrocyte progenitors

Mitochondria in oligodendrocyte progenitor cells (OPs) take up and release cytosolic Ca2+ during agonist‐evoked Ca2+ waves, but it is not clear whether or how they regulate Ca2+ signaling in OPs. We asked whether mitochondria play an active role during agonist‐evoked Ca2+ release from intracellular stores. Ca2+ puffs, wave initiation, and wave propagation were measured in fluo‐4 loaded OP processes using linescan confocal microscopy. Mitochondrial depolarization, measured by tetramethyl rhodamine ethyl ester (TMRE) fluorescence, accompanied Ca2+ puffs and waves. In addition, waves initiated only where mitochondria were localized. To determine whether energized mitochondria were necessary for wave generation, we blocked mitochondrial function with the electron transport chain inhibitor antimycin A (AA) in combination with oligomycin. AA decreased wave speed and puff probability. These effects were not due to global changes in ATP. We found that AA increased cytosolic Ca2+, markedly reduced agonist‐evoked inositol trisphosphate (IP3) production, and also enhanced phosphatidylinositol 4,5‐bisphosphate (PIP2) binding to the Ca2+ dependent protein gelsolin. Thus, the reduction in puff probability and wave speed after AA treatment may be explained by competition for PIP2 between phospholipase C and gelsolin. Energized mitochondria and low cytosolic Ca2+ concentration may be required to maintain PIP2, a substrate for IP3 signal transduction.

Are race, ethnicity, and medical school affiliation associated with NIH R01 type 1 award probability for physician investigators?

Purpose To analyze the relationship among National Institutes of Health (NIH) R01 Type 1 applicant degree, institution type, and race/ethnicity, and application award probability. Method The authors used 2000–2006 data from the NIH IMPAC II grants database and other sources to determine which individual and institutional characteristics of applicants may affect the probability of applications being awarded funding. They used descriptive statistics and probit models to estimate correlations between race/ethnicity, degree (MD or PhD), and institution type (medical school or other institution), and application award probability, controlling for a large set of observable characteristics. Results Applications from medical schools were significantly more likely than those from other institutions to receive funding, as were applications from MDs versus PhDs. Overall, applications from blacks and Asians were less likely than those from whites to be awarded funding; however, among applications from MDs at medical schools, there was no difference in funding probability between whites and Asians, and the difference between blacks and whites decreased to 7.8%. The inclusion of human subjects significantly decreased the likelihood of receiving funding. Conclusions Compared with applications from whites, applications from blacks have a lower probability of being awarded R01 Type 1 funding, regardless of the investigator’s degree. However, funding probability is increased for applications with MD investigators and for those from medical schools. To some degree, these advantages combine so that applications from black MDs at medical schools have the smallest difference in funding probability compared with those from whites.

Regional changes in central monoamine and metabolite levels during the hibernation cycle in the golden-mantled ground squirrel

We assayed various brain regions for levels of monoamines and their metabolites throughout the hibernation cycle of the golden-mantled ground squirrel Spermophilus lateralis. The tissue concentrations of serotonin, dopamine, norepinephrine and their metabolites were determined in the parietal cortex, striatum, midbrain, hippocampus, hypothalamus, and pons. Telencephalic regions exhibited the most significant variations in biogenic amine content. Cortical serotonin (5-HT) levels increased significantly at entrance (P less than 0.0001) relative to other periods of the hibernation cycle, suggesting a role for 5-HT in the initiation of hibernation. Among striatal dopamine (DA) metabolites, 3-methoxytyramine was detectable only during euthermia and arousal; from entrance through arousal, homovanillic acid (HVA) levels were half that found during euthermia (P = 0.0001); and dihydroxyphenylacetic acid (DOPAC) levels increased during day 1 of hibernation (P less than 0.0005). Midbrain DA (P = 0.0295) and hippocampal HVA (P = 0.0194) levels also changed significantly across the hibernation bout. The absence of a consistent change in any monoamine or metabolite throughout the brain precludes the possibility of preferential temperature-dependent impairment of an enzyme involved in biogenic amine synthesis or degradation and suggests that the levels observed reflect changes in neural activity specific to each brain region. Together with previous studies of brain 2-deoxyglucose uptake throughout the hibernation cycle, these data indicate that a transient change in afferent monoaminergic metabolism and neurotransmission in the forebrain is a necessary component for the entrance to hibernation.

Standards and Infrastructure for Innovation Data Exchange

Data on the global R&D enterprise are inconsistently structured and shared, which hinders understanding and policy. Economic growth relies in part on efficient advancement and application of research and development (R&D) knowledge. This requires access to data about science—in particular, R&D inputs and outputs such as grants, patents, publications, and data sets, to support an understanding of how R&D information is produced and what affects its availability. But there is a cacophony of R&D-related data across countries, disciplines, data providers, and sectors. Burdened with data that are inconsistently specified, researchers and policy-makers have few incentives or mechanisms to share or interlink cleaned data sets. Access to these data is limited by a patchwork of laws, regulations, and practices that are unevenly applied and interpreted (1). A Web-based infrastructure for data sharing and analysis could help. Data exchange standards are a first step. We describe administrative and technical demands and opportunities to meet them.