radish encodes a phospholipase-A2 and defines a neural circuit involved in anesthesia-resistant memory.

BACKGROUND: In both vertebrate and invertebrate animals, anesthetic agents cause retrograde amnesia for recently experienced events. In contrast, older memories are resistant to the same treatments. In Drosophila, anesthesia-resistant memory (ARM) and long-term memory (LTM) are genetically distinct forms of long-lasting memory that exist in parallel for at least a day after training. ARM is disrupted in radish mutants but is normal in transgenic flies overexpressing a CREB repressor transgene. In contrast, LTM is normal in radish mutants but is disrupted in CREB repressor transgenic flies. To date, nothing is known about the molecular, genetic, or cell biological pathways underlying ARM. RESULTS: Here, we report the molecular identification of radish as a phospholipase-A2, providing the first clue about signaling pathways underlying ARM in any animal. An enhancer-trap allele of radish (C133) reveals expression in a novel anatomical pathway. Transgenic expression of PLA2 under control of C133 restores normal levels of ARM to radish mutants, whereas transient disruption of neural activity in C133 neurons inhibits memory retention. Notably, expression of C133 is not in mushroom bodies, the primary anatomical focus of olfactory memory research in Drosophila. CONCLUSIONS: Identification of radish as a phospholipase-A2 and the neural expression pattern of an enhancer-trap allele significantly broaden our understanding of the biochemistry and anatomy underlying olfactory memory in Drosophila.

The Transgenic RNAi Project at Harvard Medical School: Resources and Validation.

To facilitate large-scale functional studies in Drosophila, the Drosophila Transgenic RNAi Project (TRiP) at Harvard Medical School (HMS) was established along with several goals: developing efficient vectors for RNAi that work in all tissues, generating a genome-scale collection of RNAi stocks with input from the community, distributing the lines as they are generated through existing stock centers, validating as many lines as possible using RT-qPCR and phenotypic analyses, and developing tools and web resources for identifying RNAi lines and retrieving existing information on their quality. With these goals in mind, here we describe in detail the various tools we developed and the status of the collection, which is currently composed of 11,491 lines and covering 71% of Drosophila genes. Data on the characterization of the lines either by RT-qPCR or phenotype is available on a dedicated website, the RNAi Stock Validation and Phenotypes Project (RSVP, http://www.flyrnai.org/RSVP.html), and stocks are available from three stock centers, the Bloomington Drosophila Stock Center (United States), National Institute of Genetics (Japan), and TsingHua Fly Center (China).

Regional correlation of emphysematous changes in lung function and structure: a comparison between pulmonary function testing and hyperpolarized MRI metrics.

Regional and global relationships of lung function and structure were studied using hyperpolarized ³He MRI in a rat elastase-induced model of emphysema (n = 4) and healthy controls (n = 5). Fractional ventilation (r) and apparent diffusion coefficient (ADC) of ³He were measured at a submillimeter planar resolution in ventral, middle, and dorsal slices 6 mo after model induction. Pulmonary function testing (PFT) was performed before MRI to yield forced expiratory volume in 50 ms (FEV50), airway resistance (R(I)), and dynamic compliance (C(dyn)). Cutoff threshold values of ventilation and diffusion, r* and ADC*, were computed corresponding to 80% population of pixels falling above or below each threshold value, respectively. For correlation analysis, r* was compared with FEV50/functional residual capacity (FRC), R(I) and C(dyn), whereas ADC* was compared with FEV50/FRC, total lung capacity (TLC), and C(dyn). Regional correlation of r and ADC was evaluated by dividing each of the three lung slices into four quadrants. C(dyn) was significantly larger in elastase rats (0.92 ± 0.16 vs. 0.61 ± 0.12 ml/cmH2O). The difference of R(I) and FEV50 was insignificant between the two groups. The r* of healthy rats was significantly larger than the elastase group (0.42 ± 0.03 vs. 0.28 ± 0.06), whereas ADC* was significantly smaller in healthy animals (0.27 ± 0.04 vs. 0.36 ± 0.01 cm²/s). No systematic difference in these quantities was observed between the three lung slices. A significant 33% increase in ADC* and a significant 31% decline in r* for elastase rats was observed compared with a significant 51% increase in C(dyn) and a nonsignificant 26% decline in FEV50/FRC. Correlation of imaging and PFT metrics revealed that r and ADC divide the rats into two separate clusters in the sample space.

Parallel processing of olfactory memories in Drosophila.

One of the hallmarks of both memory and the underlying synaptic plasticity is that they each rely on short-lived and longer-lived forms. Short-lived memory is thought to rely on modification to existing proteins, whereas long-term memory requires induction of new gene expression. The most common view is that these two processes rely on signaling mechanisms within the same neurons. We recently demonstrated a dissection of the signaling requirements for short and long-lived memory into distinct sets of neurons. Using an aversive olfactory conditioning task in Drosophila, we found that cAMP signaling in different neuron cell types is sufficient to support short or long-term memory independently.

Short- and long-term memory in Drosophila require cAMP signaling in distinct neuron types.

BACKGROUND: A common feature of memory and its underlying synaptic plasticity is that each can be dissected into short-lived forms involving modification or trafficking of existing proteins and long-term forms that require new gene expression. An underlying assumption of this cellular view of memory consolidation is that these different mechanisms occur within a single neuron. At the neuroanatomical level, however, different temporal stages of memory can engage distinct neural circuits, a notion that has not been conceptually integrated with the cellular view. RESULTS: Here, we investigated this issue in the context of aversive Pavlovian olfactory memory in Drosophila. Previous studies have demonstrated a central role for cAMP signaling in the mushroom body (MB). The Ca(2+)-responsive adenylyl cyclase RUTABAGA is believed to be a coincidence detector in gamma neurons, one of the three principle classes of MB Kenyon cells. We were able to separately restore short-term or long-term memory to a rutabaga mutant with expression of rutabaga in different subsets of MB neurons. CONCLUSIONS: Our findings suggest a model in which the learning experience initiates two parallel associations: a short-lived trace in MB gamma neurons, and a long-lived trace in alpha/beta neurons.

Effect of aryl ring fluorination on the antibacterial properties of C4 aryl-substituted N-methylthio beta-lactams.

4-Aryl-substituted N-thiolated beta-lactams are a new family of antibacterial agents possessing unique structure-activity profiles and a mode of action. Unlike traditional beta-lactam antibiotics, which require highly polar enzyme-binding groups, these lactams bear hydrophobic groups on their side chains. In this study, we examine the effect that increasing hydrophobicity, through fluorine substitution in the C(4) aryl ring, has on the antibacterial properties.