Forgotten memory storage and retrieval in Drosophila

Inaccessibility of stored memory in ensemble cells through the forgetting process causes animals to be unable to respond to natural recalling cues. While accumulating evidence has demonstrated that reactivating memory-stored cells can switch cells from an inaccessible state to an accessible form and lead to recall of previously learned information, the underlying cellular and molecular mechanisms remain elusive. The current study used Drosophila as a model to demonstrate that the memory of one-trial aversive olfactory conditioning, although inaccessible within a few hours after learning, is stored in KCαβ and retrievable after mild retraining. One-trial aversive conditioning triggers protein synthesis to form a long-lasting cellular memory trace, approximately 20 days, via creb in KCαβ, and a transient cellular memory trace, approximately one day, via orb in MBON-α3. PPL1-α3 negatively regulates forgotten one-trial conditioning memory retrieval. The current study demonstrated that KCαβ, PPL1-α3, and MBON-α3 collaboratively regulate the formation of forgotten one-cycle aversive conditioning memory formation and retrieval.

IMD signaling in the gut and the brain modulates Amyloid-beta-induced deficits in Drosophila

AIMS

Evidence indicates accumulating Aβ peptides in brain activates immune responses in neuronal and peripheral system, which may collaboratively influence pathogenesis of Alzheimer's disease (AD). We aim to investigate whether regulating intestinal innate immune signaling ameliorates Aβ-induced impairments in Drosophila melanogaster.

MAIN METHODS

Quantitative polymerase chain reaction (qPCR) was used to observe expression changes of innate immune responses related genes in brain and in gut under the circumstance of Aβ overexpressing in nerve system. Aversive olfactory conditioning and survival assay were used to investigate effects of modulating Attacin-A (AttA) and Dpitercin-A (DptA). Fluorometric assays of respiratory burst activity was introduced to explore whether reducing oxidative stress enables overexpressing intestinal AttA and DptA to reverse Aβ-induced deficits.

KEY FINDINGS

In vivo genetic analysis revealed that accumulating Aβ42 in neurons modulates innate immune signaling of the IMD pathway both in the brain and in the gut. Increased expression levels of the intestinal AttA and DptA improved learning performance and extended the lifespan of Aβ42 flies. The administration of apramycin led to alleviations of Aβ-induced behavioral changes, indicating that gram-negative bacteria are associated with the development of Aβ-induced pathologies. Further analysis showed that the neural expression of Aβ42 increased oxidative stress in the gut, which disrupted intestinal integrity and decreased learning performance. In addition, increased levels of AMPs targeting gram-negative bacteria and antioxidants reduced oxidative stress in the gut and reversed Aβ-induced behavioral damage.

SIGNIFICANCE

These findings suggest that innate immune responses in the gut play a pivotal role in modulating Aβ-induced pathologies.

Aversive conditioning information transmission in Drosophila

Animals rapidly acquire surrounding information to perform the appropriate behavior. Although social learning is more efficient and accessible than self-learning for animals, the detailed regulatory mechanism of social learning remains unknown, mainly because of the complicated information transfer between animals, especially for aversive conditioning information transmission. The current study revealed that, during social learning, the neural circuit in observer flies used to process acquired aversive conditioning information from demonstrator flies differs from the circuit used for self-learned classic aversive conditioning. This aversive information transfer is species dependent. Solitary flies cannot learn this information through social learning, suggesting that this ability is not an innate behavior. Neurons used to process and execute avoidance behavior to escape from electrically shocked flies are all in the same brain region, indicating that the fly brain has a common center for integrating external stimuli with internal states to generate flight behavior.

Temporal focusing multiphoton microscopy with cross-modality multi-stage 3D U-Net for fast and clear bioimaging

Temporal focusing multiphoton excitation microscopy (TFMPEM) enables fast widefield biotissue imaging with optical sectioning. However, under widefield illumination, the imaging performance is severely degraded by scattering effects, which induce signal crosstalk and a low signal-to-noise ratio in the detection process, particularly when imaging deep layers. Accordingly, the present study proposes a cross-modality learning-based neural network method for performing image registration and restoration. In the proposed method, the point-scanning multiphoton excitation microscopy images are registered to the TFMPEM images by an unsupervised U-Net model based on a global linear affine transformation process and local VoxelMorph registration network. A multi-stage 3D U-Net model with a cross-stage feature fusion mechanism and self-supervised attention module is then used to infer in-vitro fixed TFMPEM volumetric images. The experimental results obtained for in-vitro drosophila mushroom body (MB) images show that the proposed method improves the structure similarity index measures (SSIMs) of the TFMPEM images acquired with a 10-ms exposure time from 0.38 to 0.93 and 0.80 for shallow- and deep-layer images, respectively. A 3D U-Net model, pretrained on in-vitro images, is further trained using a small in-vivo MB image dataset. The transfer learning network improves the SSIMs of in-vivo drosophila MB images captured with a 1-ms exposure time to 0.97 and 0.94 for shallow and deep layers, respectively.

Early Aβ42 Exposure Causes Learning Impairment in Later Life

Amyloid cascade hypothesis proposes that amyloid β (Aβ) accumulation is the initiator and major contributor to the development of Alzheimer’s disease (AD). However, this hypothesis has recently been challenged by clinical studies showing that reduction of Aβ accumulation in the brain does not accompany with cognitive improvement, suggesting that therapeutically targeting Aβ in the brain may not be sufficient for restoring cognitive function. Since the molecular mechanism underlying the progressive development of cognitive impairment after Aβ clearance is largely unknown, the reason of why there is no behavioral improvement after Aβ clearance remains elusive. In the current study, we demonstrated that transient Aβ expression caused learning deficit in later life, despite the accumulated Aβ was soon being removed after the expression. Early Aβ exposure decreased the cellular expression of XBP1 and both the antioxidants, catalase, and dPrx5, which made cells more vulnerable to oxidative stress in later life. Early induction of XBP1, catalase, and dPrx5 prevented the overproduction of ROS, improved the learning performance, and preserved the viability of cells in the later life with the early Aβ induction. Treating the early Aβ exposed flies with antioxidants such as vitamin E, melatonin and lipoic acid, after the removal of Aβ also preserved the learning ability in later life. Taken together, we demonstrated that early and transient Aβ exposure can have a profound impact on animal behavior in later life and also revealed the cellular and molecular mechanism underlying the development of learning impairment by the early and transient Aβ exposure.

The double-edged sword effect of HDAC6 in Aβ toxicities

Alzheimer's disease (AD) is marked by cognitive impairment, massive cell death, and reduced life expectancy. Pathologically, accumulated beta-amyloid (Aβ) aggregates and hyperphosphorylated tau protein is the hallmark of the disease. Although changes in cellular function and protein accumulates have been demonstrated in many different AD animal models, the molecular mechanism involved in different cellular functions and the correlation and causative relation between different protein accumulations remain elusive. Our in vivo genetic studies revealed that the molecular mechanisms involved in memory loss and lifespan shortening are different and that tau plays an essential role in mediating Aβ-induced early death. We found that when the first deacetylase (DAC) domain of histone deacetylase 6 (HDAC6) activity was increased, it regulated cortactin deacetylation to reverse Aβ-induced learning and memory deficit, but with no effect on the lifespan of the Aβ flies. On the other hand, an increased amount of the second DAC domain of HDAC6 promoted tau phosphorylation to facilitate Aβ-induced lifespan shortening without affecting learning performance in the Aβ flies. Our data also confirmed decreased acetylation in two major HDAC6 downstream proteins, suggesting increased HDAC6 activity in Aβ flies. Our data established the double-edged sword effect of HDAC6 activity in Aβ-induced pathologies. Not only did we segregate memory loss and lifespan shortening in Aβ flies, but we also provided evidence to link the Aβ with tau signaling.

Rac1 and Akt Exhibit Distinct Roles in Mediating Aβ-Induced Memory Damage and Learning Impairment

Accumulated beta-amyloid (Aβ) in the brain is the hallmark of Alzheimer's disease (AD). Despite Aβ accumulation is known to trigger cellular dysfunctions and learning and memory damage, the detailed molecular mechanism remains elusive. Recent studies have shown that the onset of memory impairment and learning damage in the AD animal is different, suggesting that the underlying mechanism of the development of memory impairment and learning damage may not be the same. In the current study, with the use of Aβ42 transgenic flies as models, we found that Aβ induces memory damage and learning impairment via differential molecular signaling pathways. In early stage, Aβ activates both Ras and PI3K to regulate Rac1 activity, which affects mostly on memory performance. In later stage, PI3K-Akt is strongly activated by Aβ, which leads to learning damage. Moreover, reduced Akt, but not Rac1, activity promotes cell viability in the Aβ42 transgenic flies, indicating that Akt and Rac1 exhibit differential roles in Aβ regulating toxicity. Taken together, different molecular and cellular mechanisms are involved in Aβ-induced learning damage and memory decline; thus, caution should be taken during the development of therapeutic intervention in the future.

Mushroom body subsets encode CREB2-dependent water-reward long-term memory in Drosophila

Long-term memory (LTM) formation depends on the conversed cAMP response element-binding protein (CREB)-dependent gene transcription followed by de novo protein synthesis. Thirsty fruit flies can be trained to associate an odor with water reward to form water-reward LTM (wLTM), which can last for over 24 hours without a significant decline. The role of de novo protein synthesis and CREB-regulated gene expression changes in neural circuits that contribute to wLTM remains unclear. Here, we show that acute inhibition of protein synthesis in the mushroom body (MB) αβ or γ neurons during memory formation using a cold-sensitive ribosome-inactivating toxin disrupts wLTM. Furthermore, adult stage-specific expression of dCREB2b in αβ or γ neurons also disrupts wLTM. The MB αβ and γ neurons can be further classified into five different neuronal subsets including αβ core, αβ surface, αβ posterior, γ main, and γ dorsal. We observed that the neurotransmission from αβ surface and γ dorsal neuron subsets is required for wLTM retrieval, whereas the αβ core, αβ posterior, and γ main are dispensable. Adult stage-specific expression of dCREB2b in αβ surface and γ dorsal neurons inhibits wLTM formation. In vivo calcium imaging revealed that αβ surface and γ dorsal neurons form wLTM traces with different dynamic properties, and these memory traces are abolished by dCREB2b expression. Our results suggest that a small population of neurons within the MB circuits support long-term storage of water-reward memory in Drosophila.

The C-Band All-Sky Survey (C-BASS): Simulated parametric fitting in single pixels in total intensity and polarization

The cosmic microwave background (CMB) B-mode signal is potentially weaker than the diffuse Galactic foregrounds over most of the sky at any frequency. A common method of separating the CMB from these foregrounds is via pixel-based parametric-model fitting. There are not currently enough all-sky maps to fit anything more than the most simple models of the sky. By simulating the emission in seven representative pixels, we demonstrate that the inclusion of a 5 GHz data point allows for more complex models of low-frequency foregrounds to be fitted than at present. It is shown that the inclusion of the C-BASS data will significantly reduce the uncertainties in a number of key parameters in the modelling of both the galactic foregrounds and the CMB. The extra data allow estimates of the synchrotron spectral index to be constrained much more strongly than is presently possible, with corresponding improvements in the accuracy of the recovery of the CMB amplitude. However, we show that to place good limits on models of the synchrotron spectral curvature will require additional low-frequency data.

Detection of CMB-Cluster Lensing using Polarization Data from SPTpol

We report the first detection of gravitational lensing due to galaxy clusters using only the polarization of the cosmic microwave background (CMB). The lensing signal is obtained using a new estimator that extracts the lensing dipole signature from stacked images formed by rotating the cluster-centered Stokes QU map cutouts along the direction of the locally measured background CMB polarization gradient. Using data from the SPTpol 500  deg^{2} survey at the locations of roughly 18 000 clusters with richness λ≥10 from the Dark Energy Survey (DES) Year-3 full galaxy cluster catalog, we detect lensing at 4.8σ. The mean stacked mass of the selected sample is found to be (1.43±0.40)×10^{14}M_{⊙} which is in good agreement with optical weak lensing based estimates using DES data and CMB-lensing based estimates using SPTpol temperature data. This measurement is a key first step for cluster cosmology with future low-noise CMB surveys, like CMB-S4, for which CMB polarization will be the primary channel for cluster lensing measurements.

Aging-induced Akt activation involves in aging-related pathologies and Aβ-induced toxicity

Multicellular signals are altered in the processes of both aging and neurodegenerative diseases, including Alzheimer's disease (AD). Similarities in behavioral and cellular functional changes suggest a common regulator between aging and AD that remains undetermined. Our genetics and behavioral approaches revealed the regulatory role of Akt in both aging and AD pathogenesis. In this study, we found that the activity of Akt is upregulated during aging through epidermal growth factor receptor activation by using the fruit fly as an in vivo model. Downregulation of Akt in neurons improved cell survival, locomotor activity, and starvation challenge in both aged and Aβ42‐expressing flies. Interestingly, increased cAMP levels attenuated both Akt activation‐induced early death and Aβ42‐induced learning deficit in flies. At the molecular level, overexpression of Akt promoted Notch cleavage, suggesting that Akt is an endogenous activity regulator of γ‐secretase. Taken together, this study revealed that Akt is involved in the aging process and Aβ toxicity, and manipulating Akt can restore both neuronal functions and improve behavioral activity during the processes of aging and AD pathogenesis.

Electrical synapses between mushroom body neurons are critical for consolidated memory retrieval in Drosophila

Electrical synapses between neurons, also known as gap junctions, are direct cell membrane channels between adjacent neurons. Gap junctions play a role in the synchronization of neuronal network activity; however, their involvement in cognition has not been well characterized. Three-hour olfactory associative memory in Drosophila has two components: consolidated anesthesia-resistant memory (ARM) and labile anesthesia-sensitive memory (ASM). Here, we show that knockdown of the gap junction gene innexin5 (inx5) in mushroom body (MB) neurons disrupted ARM, while leaving ASM intact. Whole-mount brain immunohistochemistry indicated that INX5 protein was preferentially expressed in the somas, calyxes, and lobes regions of the MB neurons. Adult-stage-specific knockdown of inx5 in αβ neurons disrupted ARM, suggesting a specific requirement of INX5 in αβ neurons for ARM formation. Hyperpolarization of αβ neurons during memory retrieval by expressing an engineered halorhodopsin (eNpHR) also disrupted ARM. Administration of the gap junction blocker carbenoxolone (CBX) reduced the proportion of odor responsive αβ neurons to the training odor 3 hours after training. Finally, the α-branch-specific 3-hour ARM-specific memory trace was also diminished with CBX treatment and in inx5 knockdown flies. Altogether, our results suggest INX5 gap junction channels in αβ neurons for ARM retrieval and also provide a more detailed neuronal mechanism for consolidated memory in Drosophila.

Visualization of Membrane Pore in Live Cells Reveals a Dynamic-Pore Theory Governing Fusion and Endocytosis

Fusion is thought to open a pore to release vesicular cargoes vital for many biological processes, including exocytosis, intracellular trafficking, fertilization, and viral entry. However, fusion pores have not been observed and thus proved in live cells. Its regulatory mechanisms and functions remain poorly understood. With super-resolution STED microscopy, we observed dynamic fusion pore behaviors in live (neuroendocrine) cells, including opening, expansion, constriction, and closure, where pore size may vary between 0 and 490 nm within 26 milliseconds to seconds (vesicle size: 180-720 nm). These pore dynamics crucially determine the efficiency of vesicular cargo release and vesicle retrieval. They are generated by competition between pore expansion and constriction. Pharmacology and mutation experiments suggest that expansion and constriction are mediated by F-actin-dependent membrane tension and calcium/dynamin, respectively. These findings provide the missing live-cell evidence, proving the fusion-pore hypothesis, and establish a live-cell dynamic-pore theory accounting for fusion, fission, and their regulation.

Mushroom body glycolysis is required for olfactory memory in Drosophila

Glucose catabolism, also known as glycolysis, is important for energy generation and involves a sequence of enzymatic reactions that convert a glucose molecule into two pyruvate molecules. The glycolysis process generates adenosine triphosphate as a byproduct. In this study, we investigated whether glycolysis plays a role in maintaining neuronal functions in the Drosophila mushroom bodies (MBs), which are generally accepted to be an olfactory learning and memory center. Our data showed that individual knockdown of glycolytic enzymes in the MBs, including hexokinase (HexA), phosphofructokinase (Pfk), or pyruvate kinase (PyK), disrupts olfactory memory. Whole-mount brain immunostaining indicated that pyruvate kinase is strongly expressed in the MB αβ, α'β', and γ neuron subsets. We conclude that HexA, Pfk, and PyK are required in each MB neuron subset for olfactory memory formation. Our data therefore indicates that glucose catabolism in the MBs is important for olfactory memory formation in Drosophila.

Dysfunction of different cellular degradation pathways contributes to specific β-amyloid42-induced pathologies

The endosomal-lysosomal system (ELS), autophagy, and ubiquitin-proteasome system (UPS) are cellular degradation pathways that each play a critical role in the removal of misfolded proteins and the prevention of the accumulation of abnormal proteins. Recent studies on Alzheimer's disease (AD) pathogenesis have suggested that accumulation of aggregated β-amyloid (Aβ) peptides in the AD brain results from a dysfunction in these cellular clearance systems. However, the specific roles of these pathways in the removal of Aβ peptides and the pathogenesis underlying AD are unclear. Our in vitro and in vivo genetic approaches revealed that ELS mainly removed monomeric β-amyloid42 (Aβ42), while autophagy and UPS clear oligomeric Aβ42. Although overproduction of phosphatidylinositol 4-phosphate-5 increased Aβ42 clearance, it reduced the life span of Aβ42 transgenic flies. Our behavioral studies further demonstrated impaired autophagy and UPS-enhanced Aβ42-induced learning and memory deficits, but there was no effect on Aβ42-induced reduction in life span. Results from genetic fluorescence imaging showed that these pathways were damaged in the following order: UPS, autophagy, and finally ELS. The results of our study demonstrate that different degradation pathways play distinct roles in the removal of Aβ42 aggregates and in disease progression. These findings also suggest that pharmacologic treatments that are designed to stimulate cellular degradation pathways in patients with AD should be used with caution.-Ji, X.-R., Cheng, K.-C., Chen, Y.-R., Lin, T.-Y., Cheung, C. H. A., Wu, C.-L., Chiang, H.-C. Dysfunction of different cellular degradation pathways contributes to specific β-amyloid42-induced pathologies.

Actin dynamics provides membrane tension to merge fusing vesicles into the plasma membrane

Vesicle fusion is executed via formation of an Ω-shaped structure (Ω-profile), followed by closure (kiss-and-run) or merging of the Ω-profile into the plasma membrane (full fusion). Although Ω-profile closure limits release but recycles vesicles economically, Ω-profile merging facilitates release but couples to classical endocytosis for recycling. Despite its crucial role in determining exocytosis/endocytosis modes, how Ω-profile merging is mediated is poorly understood in endocrine cells and neurons containing small ∼30–300 nm vesicles. Here, using confocal and super-resolution STED imaging, force measurements, pharmacology and gene knockout, we show that dynamic assembly of filamentous actin, involving ATP hydrolysis, N-WASP and formin, mediates Ω-profile merging by providing sufficient plasma membrane tension to shrink the Ω-profile in neuroendocrine chromaffin cells containing ∼300 nm vesicles. Actin-directed compounds also induce Ω-profile accumulation at lamprey synaptic active zones, suggesting that actin may mediate Ω-profile merging at synapses. These results uncover molecular and biophysical mechanisms underlying Ω-profile merging.

As vesicles fuse to the plasma membrane, they form intermediate Ω-shaped structures followed by either closure of the pore or full merging with the plasma membrane. Here Wen et al. show that dynamic actin assembly provides membrane tension to promote Ω merging in neuroendocrine cells and synapses.

Hemi-fused structure mediates and controls fusion and fission in live cells

Membrane fusion and fission are vital for eukaryotic life. For three decades, it has been proposed that fusion is mediated by fusion between the proximal leaflets of two bilayers (hemi-fusion) to produce a hemi-fused structure, followed by fusion between the distal leaflets, whereas fission is via hemi-fission, which also produces a hemi-fused structure, followed by full fission. This hypothesis remained unsupported owing to the lack of observation of hemi-fusion or hemi-fission in live cells. A competing fusion hypothesis involving protein-lined pore formation has also been proposed. Here we report the observation of a hemi-fused Ω-shaped structure in live neuroendocrine chromaffin cells and pancreatic β-cells, visualized using confocal and super-resolution stimulated emission depletion microscopy. This structure is generated from fusion pore opening or closure (fission) at the plasma membrane. Unexpectedly, the transition to full fusion or fission is determined by competition between fusion and calcium/dynamin-dependent fission mechanisms, and is notably slow (seconds to tens of seconds) in a substantial fraction of the events. These results provide key missing evidence in support of the hemi-fusion and hemi-fission hypothesis in live cells, and reveal the hemi-fused intermediate as a key structure controlling fusion and fission, as fusion and fission mechanisms compete to determine the transition to fusion or fission.

Joint analysis of BICEP2/keck array and Planck Data

We report the results of a joint analysis of data from BICEP2/Keck Array and Planck. BICEP2 and Keck Array have observed the same approximately 400  deg^{2} patch of sky centered on RA 0 h, Dec. -57.5°. The combined maps reach a depth of 57 nK deg in Stokes Q and U in a band centered at 150 GHz. Planck has observed the full sky in polarization at seven frequencies from 30 to 353 GHz, but much less deeply in any given region (1.2  μK deg in Q and U at 143 GHz). We detect 150×353 cross-correlation in B modes at high significance. We fit the single- and cross-frequency power spectra at frequencies ≥150  GHz to a lensed-ΛCDM model that includes dust and a possible contribution from inflationary gravitational waves (as parametrized by the tensor-to-scalar ratio r), using a prior on the frequency spectral behavior of polarized dust emission from previous Planck analysis of other regions of the sky. We find strong evidence for dust and no statistically significant evidence for tensor modes. We probe various model variations and extensions, including adding a synchrotron component in combination with lower frequency data, and find that these make little difference to the r constraint. Finally, we present an alternative analysis which is similar to a map-based cleaning of the dust contribution, and show that this gives similar constraints. The final result is expressed as a likelihood curve for r, and yields an upper limit r_{0.05}<0.12 at 95% confidence. Marginalizing over dust and r, lensing B modes are detected at 7.0σ significance.

Exocytosis and endocytosis: modes, functions, and coupling mechanisms

Vesicle exocytosis releases content to mediate many biological events, including synaptic transmission essential for brain functions. Following exocytosis, endocytosis is initiated to retrieve exocytosed vesicles within seconds to minutes. Decades of studies in secretory cells reveal three exocytosis modes coupled to three endocytosis modes: (a) full-collapse fusion, in which vesicles collapse into the plasma membrane, followed by classical endocytosis involving membrane invagination and vesicle reformation; (b) kiss-and-run, in which the fusion pore opens and closes; and (c) compound exocytosis, which involves exocytosis of giant vesicles formed via vesicle-vesicle fusion, followed by bulk endocytosis that retrieves giant vesicles. Here we review these exo- and endocytosis modes and their roles in regulating quantal size and synaptic strength, generating synaptic plasticity, maintaining exocytosis, and clearing release sites for vesicle replenishment. Furthermore, we highlight recent progress in understanding how vesicle endocytosis is initiated and is thus coupled to exocytosis. The emerging model is that calcium influx via voltage-dependent calcium channels at the calcium microdomain triggers endocytosis and controls endocytosis rate; calmodulin and synaptotagmin are the calcium sensors; and the exocytosis machinery, including SNARE proteins (synaptobrevin, SNAP25, and syntaxin), is needed to coinitiate endocytosis, likely to control the amount of endocytosis.

Detection of B-mode polarization in the cosmic microwave background with data from the South Pole Telescope

Gravitational lensing of the cosmic microwave background generates a curl pattern in the observed polarization. This "B-mode" signal provides a measure of the projected mass distribution over the entire observable Universe and also acts as a contaminant for the measurement of primordial gravity-wave signals. In this Letter we present the first detection of gravitational lensing B modes, using first-season data from the polarization-sensitive receiver on the South Pole Telescope (SPTpol). We construct a template for the lensing B-mode signal by combining E-mode polarization measured by SPTpol with estimates of the lensing potential from a Herschel-SPIRE map of the cosmic infrared background. We compare this template to the B modes measured directly by SPTpol, finding a nonzero correlation at 7.7σ significance. The correlation has an amplitude and scale dependence consistent with theoretical expectations, is robust with respect to analysis choices, and constitutes the first measurement of a powerful cosmological observable.

Distinctive roles of different beta-amyloid 42 aggregates in modulation of synaptic functions

To determine how endogenously secreted beta-amyloid 42 (Abeta42) aggregates regulate synaptic functions, we examined effects of Abeta42 at the neuromuscular junction of Drosophila larvae. Voltage-clamp recordings of synaptic transmission and optical analysis of vesicle recycling at presynaptic terminals show that expression of Abeta42 in neurons leads to a reduction of neurotransmitter release. However, expression of Abeta42 in postsynaptic muscle cells enhanced neurotransmitter release. Both effects are neutralized by Abeta antibody, suggesting a role for secreted Abeta42 peptides. Application of exogenously prepared Abeta42 oligomers leads to a reduction in synaptic responses, whereas mixed Abeta42 aggregates with mainly fibrils elicit an opposite effect by increasing synaptic transmission. Further analysis of long-term depression (LTD) confirms differential effects of different Abeta42 aggregates. Taken together, our data suggest that Abeta42 is secreted from neurons primarily as oligomers that inhibit neurotransmitter release and exert no effect on LTD. Whereas larger-sized aggregates, possibly fibrils, are major components secreted from muscle cells, which enhance synaptic transmission and LTD. Thus, different types of cells may secrete distinct forms of Abeta42 aggregates, leading to different modulation of synaptic functions.

Overexpression of neprilysin reduces alzheimer amyloid-beta42 (Abeta42)-induced neuron loss and intraneuronal Abeta42 deposits but causes a reduction in cAMP-responsive element-binding protein-mediated transcription, age-dependent axon pathology, and premature death in Drosophila

The amyloid-beta42 (Abeta42) peptide has been suggested to play a causative role in Alzheimer disease (AD). Neprilysin (NEP) is one of the rate-limiting Abeta-degrading enzymes, and its enhancement ameliorates extracellular amyloid pathology, synaptic dysfunction, and memory defects in mouse models of Abeta amyloidosis. In addition to the extracellular Abeta, intraneuronal Abeta42 may contribute to AD pathogenesis. However, the protective effects of neuronal NEP expression on intraneuronal Abeta42 accumulation and neurodegeneration remain elusive. In contrast, sustained NEP activation may be detrimental because NEP can degrade many physiological peptides, but its consequences in the brain are not fully understood. Using transgenic Drosophila expressing human NEP and Abeta42, we demonstrated that NEP efficiently suppressed the formation of intraneuronal Abeta42 deposits and Abeta42-induced neuron loss. However, neuronal NEP overexpression reduced cAMP-responsive element-binding protein-mediated transcription, caused age-dependent axon degeneration, and shortened the life span of the flies. Interestingly, the mRNA levels of endogenous fly NEP genes and phosphoramidon-sensitive NEP activity declined during aging in fly brains, as observed in mammals. Taken together, these data suggest both the protective and detrimental effects of chronically high NEP activity in the brain. Down-regulation of NEP activity in aging brains may be an evolutionarily conserved phenomenon, which could predispose humans to developing late-onset AD.

Abeta42 mutants with different aggregation profiles induce distinct pathologies in Drosophila

Aggregation of the amyloid-β-42 (Aβ42) peptide in the brain parenchyma is a pathological hallmark of Alzheimer's disease (AD), and the prevention of Aβ aggregation has been proposed as a therapeutic intervention in AD. However, recent reports indicate that Aβ can form several different prefibrillar and fibrillar aggregates and that each aggregate may confer different pathogenic effects, suggesting that manipulation of Aβ42 aggregation may not only quantitatively but also qualitatively modify brain pathology. Here, we compare the pathogenicity of human Aβ42 mutants with differing tendencies to aggregate. We examined the aggregation-prone, EOFAD-related Arctic mutation (Aβ42Arc) and an artificial mutation (Aβ42art) that is known to suppress aggregation and toxicity of Aβ42 in vitro. In the Drosophila brain, Aβ42Arc formed more oligomers and deposits than did wild type Aβ42, while Aβ42art formed fewer oligomers and deposits. The severity of locomotor dysfunction and premature death positively correlated with the aggregation tendencies of Aβ peptides. Surprisingly, however, Aβ42art caused earlier onset of memory defects than Aβ42. More remarkably, each Aβ induced qualitatively different pathologies. Aβ42Arc caused greater neuron loss than did Aβ42, while Aβ42art flies showed the strongest neurite degeneration. This pattern of degeneration coincides with the distribution of Thioflavin S-stained Aβ aggregates: Aβ42Arc formed large deposits in the cell body, Aβ42art accumulated preferentially in the neurites, while Aβ42 accumulated in both locations. Our results demonstrate that manipulation of the aggregation propensity of Aβ42 does not simply change the level of toxicity, but can also result in qualitative shifts in the pathology induced in vivo.

B-group vitamins, MTHFR C677T polymorphism and carotid intima-media thickness in clinically healthy subjects

OBJECTIVE

Plasma B-group vitamins and age may affect the carotid intima-media thickness (IMT) in subjects with different 677TT genotype of the methylenetetrahydrofolate reductase (MTHFR) gene.

DESIGN

A hospital-based cross-study.

SETTING

Genomic and Vascular Center, Changhua Christian Hospital, Changhua, Taiwan.

SUBJECTS

Five hundred and forty-one clinically healthy subjects.

INTERVENTION

Fasting plasma, homocysteine (Hcy), vitamin B(6), vitamin B(12), folate and B-mode carotid ultrasound.

RESULTS

MTHFR genotype, plasma concentrations of folate, vitamin B(6) and vitamin B(12) and age were significantly correlated to the plasma Hcy concentration. MTHFR 677TT carriers had higher concentrations of Hcy than did subjects with the CC and CT genotypes. Age, sex, body mass index and plasma Hcy were independent contributors to increase carotid IMT. However, with stratification by mean value of age and B-group vitamins concentrations, we found that at advanced age, lower plasma folate and vitamin B(12) were three risk factors involved in the enhancing effect of the MTHFR 677TT genotype on the increase of plasma Hcy and carotid IMT.

CONCLUSION

MTHFR 677TT-related carotid atherosclerosis was only identified in healthy elderly subjects with lower level of plasma folate and vitamin B(12).

SPONSORSHIP

Changhua Christian Hospital.

Amyotrophic lateral sclerosis 2-deficiency leads to neuronal degeneration in amyotrophic lateral sclerosis through altered AMPA receptor trafficking

Amyotrophic lateral sclerosis (ALS), the most common adult-onset motor neuron disease is caused by a selective loss of motor neurons. One form of juvenile onset autosomal recessive ALS (ALS2) has been linked to the loss of function of the ALS2 gene. The pathogenic mechanism of ALS2-deficiency, however, remains unclear. To further understand the function of alsin that is encoded by the full-length ALS2 gene, we screened proteins interacting with alsin. Here, we report that alsin interacted with glutamate receptor interacting protein 1 (GRIP1) both in vitro and in vivo, and colocalized with GRIP1 in neurons. In support of the physiological interaction between alsin and GRIP1, the subcellular distribution of GRIP1 was altered in ALS2(-/-) spinal motor neurons, which correlates with a significant reduction of AMPA-type glutamate receptor subunit 2 (GluR2) at the synaptic/cell surface of ALS2(-/-) neurons. The decrease of calcium-impermeable GluR2-containing AMPA receptors at the cell/synaptic surface rendered ALS2(-/-) neurons more susceptible to glutamate receptor-mediated neurotoxicity. Our findings reveal a novel function of alsin in AMPA receptor trafficking and provide a novel pathogenic link between ALS2-deficiency and motor neuron degeneration, suggesting a protective role of alsin in maintaining the survival of motor neurons.

BACE1, a major determinant of selective vulnerability of the brain to amyloid-beta amyloidogenesis, is essential for cognitive, emotional, and synaptic functions

A transmembrane aspartyl protease termed beta-site APP cleavage enzyme 1 (BACE1) that cleaves the amyloid-beta precursor protein (APP), which is abundant in neurons, is required for the generation of amyloid-beta (Abeta) peptides implicated in the pathogenesis of Alzheimer's disease (AD). We now demonstrate that BACE1, enriched in neurons of the CNS, is a major determinant that predisposes the brain to Abeta amyloidogenesis. The physiologically high levels of BACE1 activity coupled with low levels of BACE2 and alpha-secretase anti-amyloidogenic activities in neurons is a major contributor to the accumulation of Abeta in the CNS, whereas other organs are spared. Significantly, deletion of BACE1 in APPswe;PS1DeltaE9 mice prevents both Abeta deposition and age-associated cognitive abnormalities that occur in this model of Abeta amyloidosis. Moreover, Abeta deposits are sensitive to BACE1 dosage and can be efficiently cleared from the CNS when BACE1 is silenced. However, BACE1 null mice manifest alterations in hippocampal synaptic plasticity as well as in performance on tests of cognition and emotion. Importantly, memory deficits but not emotional alterations in BACE1(-/-) mice are prevented by coexpressing APPswe;PS1DeltaE9 transgenes, indicating that other potential substrates of BACE1 may affect neural circuits related to emotion. Our results establish BACE1 and APP processing pathways as critical for cognitive, emotional, and synaptic functions, and future studies should be alert to potential mechanism-based side effects that may occur with BACE1 inhibitors designed to ameliorate Abeta amyloidosis in AD.

Loss of ALS2 function is insufficient to trigger motor neuron degeneration in knock-out mice but predisposes neurons to oxidative stress

Amyotrophic lateral sclerosis (ALS), the most common motor neuron disease, is caused by a selective loss of motor neurons in the CNS. Mutations in the ALS2 gene have been linked to one form of autosomal recessive juvenile onset ALS (ALS2). To investigate the pathogenic mechanisms of ALS2, we generated ALS2 knock-out (ALS2(-/-)) mice. Although ALS2(-/-) mice lacked obvious developmental abnormalities, they exhibited age-dependent deficits in motor coordination and motor learning. Moreover, ALS2(-/-) mice showed a higher anxiety response in the open-field and elevated plus-maze tasks. Although they failed to recapitulate clinical or neuropathological phenotypes consistent with motor neuron disease by 20 months of age, ALS2(-/-) mice or primary cultured neurons derived from these mice were more susceptible to oxidative stress compared with wild-type controls. These observations suggest that loss of ALS2 function is insufficient to cause major motor deficits or motor neuron degeneration in a mouse model but predisposes neurons to oxidative stress.

Measurement of the tensor structure function b1 of the deuteron

The Hermes experiment has investigated the tensor spin structure of the deuteron using the 27.6 GeV/c positron beam of DESY HERA. The use of a tensor-polarized deuteron gas target with only a negligible residual vector polarization enabled the first measurement of the tensor asymmetry A(d)zz and the tensor structure function b(d)1 for average values of the Bjorken variable 0.01< <x> <0.45 and of the negative of the squared four-momentum transfer 0.5 GeV2 < <Q2> <5 GeV2. The quantities A(d)zz and b(d)1 are found to be nonzero. The rise of b(d)1 for decreasing values of x can be interpreted to originate from the same mechanism that leads to nuclear shadowing in unpolarized scattering.

Synergistic effects of dopamine and Zn2+ on the induction of PC12 cell death and dopamine depletion in the striatum: possible implication in the pathogenesis of Parkinson's disease

The mechanism that underlies the progressive degeneration of the dopaminergic neurons in Parkinson's disease (PD) is not clear. The Zn(2+) level in the substantia nigra of Parkinson's patients is increased. However, it is unknown whether Zn(2+) has a role in the degeneration of dopaminergic neurons. This study identifies an interaction between dopamine and Zn(2+) that induces cell death. When PC12 cells were pretreated with Zn(2+) before dopamine treatment, dopamine and Zn(2+) synergistically increased cell death, while Zn(2+) and H(2)O(2) had only additive effects on cell death. The synergistic effect appeared to be caused by increased apoptosis rather than necrosis. The synergistic effect was specific for Zn(2+). The synergistic effect was inhibited by thiol antioxidants but was not significantly affected by calcium channel blockers. There is a similar synergistic effect when dopamine and Zn(2+) were coinfused into the striatum, resulting in striatal dopamine content depletion in vivo. Thus, both dopamine oxidation and Zn(2+) are possibly linked to the degeneration of dopaminergic neurons.

Flavor decomposition of the sea-quark helicity distributions in the nucleon from semiinclusive deep inelastic scattering

Double-spin asymmetries of semiinclusive cross sections for the production of identified pions and kaons have been measured in deep inelastic scattering of polarized positrons on a polarized deuterium target. Five helicity distributions including those for three sea quark flavors were extracted from these data together with reanalyzed previous data for identified pions from a hydrogen target. These distributions are consistent with zero for all three sea flavors. A recently predicted flavor asymmetry in the polarization of the light quark sea appears to be disfavored by the data.

Q2 dependence of nuclear transparency for exclusive rho0 production

Exclusive coherent and incoherent electroproduction of the rho(0) meson from 1H and 14N targets has been studied at the HERMES experiment as a function of coherence length (l(c)), corresponding to the lifetime of hadronic fluctuations of the virtual photon, and squared four-momentum of the virtual photon (-Q2). The ratio of 14N to 1H cross sections per nucleon, called nuclear transparency, was found to increase (decrease) with increasing l(c) for coherent (incoherent) rho(0) electroproduction. For fixed l(c), a rise of nuclear transparency with Q2 is observed for both coherent and incoherent rho(0) production, which is in agreement with theoretical calculations of color transparency.

Surgical treatment for Haglund's deformity

Haglund's deformity, or "pump bump" is a common cause of posterior heel pain, characterized clinically by a painful soft tissue swelling at the level of the Achilles tendon insertion. We reviewed 30 heels in 19 patients with failure of conservative treatment. Surgical management consisted of excision of the posterior calcaneal tuberosity and bursectomy through a medial longitudinal incision. The average follow-up period was 6 years (range, 3-10 years). Only 3 heels (10%) in 2 patients had persistent pain. Twenty-seven heels (90%) were cured after operation. However, 25 heels (83%) had residual pain for a half to two years after operation and became free of symptoms thereafter. We conclude surgical treatment of Haglund's deformity produces a predictably good result (90%) but requires a long time about a half to two years for full recovery.

Isolated talonavicular arthrodesis for talonavicular arthritis

We have reviewed a single surgeon's experience with isolated talonavicular fusion in 16 patients with talonavicular arthritis. Fixation was either by staples or screws. Fifteen solid unions were achieved in the 16 patients who were followed (mean: 51 months). The average Ankle-Hindfoot Scale improved from 77.2 preoperatively to 92.9 postoperatively (p < 0.001). Subjectively, 15 patients were satisfied and one patient dissatisfied with the results. Further osteoarthritis in the adjacent joints was noted in five patients. We concluded that isolated talonavicular fusion is an effective method of treatment of talonavicular arthritis regarding pain relief and functional improvement. Though osteoarthritis was found in some adjacent joints postoperatively, the results were still satisfactory.

Low tibial osteotomy for moderate ankle arthritis

Low tibial osteotomy is one of the significant advances of ankle reconstruction techniques that has been made recently in an effort to halt arthritis in its early stages and leave fusion as the last, not the only, alternative treatment of ankle arthritis. From 1989 to 1995, we performed 18 low tibial osteotomies which included 6 cases of post-traumatic arthritis and 12 cases of degenerative arthritis. The ages of the 7 male and 11 female patients ranged from 18 to 78 years with an average of 41.9 years. The follow-up period lasted a mean of 47.7 months, ranging from 25 to 82 months. The average functional score changed from 49.6 pre-operatively to 88.5 at the last follow up, and showed yearly improvement. Complications included one case of late infection and two cases of implant failure, none of which led to nonunion. The indication for low tibial osteotomy is the intermediate stage of moderate ankle arthritis with a medial joint lesion and intact lateral facet. Using pressure redistribution on the joint surface, this procedure is an alternative treatment for ankle arthritis which may save an arthritic ankle from the fate of fusion or at least postpone fusion surgery.

Isolation and characterization of antioxidant compounds from Aspergillus candidus broth filtrate

The objectives of this study were to isolate the antioxidative components in the broth filtrate of Aspergillus candidus (CCRC 31543), to characterize their antioxidative properties, and to evaluate their safety. Three major compounds were isolated and identified as 3,3' '-dihydroxyterphenyllin, 3-hydroxyterphenyllin, and candidusin B. In the linoleic acid peroxidation system, the inhibition of peroxidation in these three compounds was greater than 95% and was significantly higher than that of alpha-tocopherol but equal to that of BHA at 12.5-200 microg/mL. As measured using the Rancimat method in lard, 3,3' '-di-OH-terphenyllin exhibited a protection factor value of 7.82, which was substantially higher than those of BHA (5.58) and alpha-tocopherol (4.29) at 200 microg/mL. 3,3' '-di-OH-terphenyllin and 3-OH-terphenyllin also exhibited marked scavenging effects on the alpha,alpha-diphenyl-beta-picrylhydrazyl radicals (94.7 and 96.0%, respectively), which were similar to those of BHA and alpha-tocopherol. Safety studies showed that these three compounds were neither cyto- nor geno-toxic toward human intestine 407 (INT 407) cells, nor mutagenic toward Salmonella typhimurium TA98 and TA100.

Thermo-debonding mechanisms in dentin bonding systems using finite element analysis

The finite element method (FEM) has been extensively used in evaluating the interfacial status of biomaterials. We used FEM to explore the microscopic debonding mechanism of the dentin/hybrid layer/resin adhesive interface. The stress status of the local material was used as an index to judge whether the adhesive interface would develop a debonding mechanism. To generate the local stress concentration, the thermal boundary condition was applied to the model which has the phenomenon of the coefficient of thermal expansion (CTE) mismatch. The thermal boundary condition was used to emulute a previous study conducted with a laser thermoacoustic technique (LTAT). The materials, Scotchbond MP, Optibond, and Tenure bonding systems, used in the previous experiment were also tested in this study. The results show that interfacial debonding in the finite element model occurred through the hybrid layer for both the Scotchbond MP and Tenure systems, as well as within the adhesive layer itself for the Optibond system. These findings are compatible with observations by SEM obtained by LTAT. Another transformed model was created to test the "elastic cavity wall" concept. The result also confirms the importance of the elastic cavity wall concept. These compatible results between FEM and LTAT indicate that FEM can be a very useful supplement to thermoacoustic testing.

Specific induction of glutathione S-transferase GSTM2 subunit expression by epigallocatechin gallate in rat liver

The antitumor effect of green tea polyphenols has been well characterized in numerous papers. However, the mechanism of their action is still poorly defined. In this study, epigallocatechin gallate (EGCG), the main ingredient of green tea extract, was studied for its effect on the expression of glutathione S-transferases (GSTs) in rat liver to examine the mechanism of action. Liver samples were collected from Sprague-Dawley rats treated with EGCG in H(2)O by portal vein perfusion and examined for total GST activity and GST expression. The results showed that the induction of GST activity by EGCG was dose- and time-dependent. GST activity was increased about 28-fold at 12 hr after treatment. Three GST subunits (GSTA1/2, GSTM1, and GSTM2) were examined by Western blot for changes in protein level affected by EGCG (1 mg/kg weight). Only GSTM2 revealed a significant time-dependent increase, with a maximal induction of approximately 2.0-fold. The differential effect of EGCG on GST subunit expression was also verified by immunocytochemical examination and showed strong induction of the GSTM2 (but not the GSTA1/2 and GSTM1) level in liver section. This induction occurred as early as 3 hr after treatment and extended gradually outward from the hepatic veins as treatment time increased. The change in the GSTM2 protein level was accompanied by a corresponding alteration in mRNA quantity ( approximately 2.0-fold of control). Our report is the first to demonstrate a specific induction of the GSTM2 subunit by a chemopreventor and suggests a primary influence of EGCG on GSTM2 gene expression.

Finite element analysis of thermo-debonding mechanism in dental composites

Finite element method (FEM) has been extensively used for evaluating interfacial status inside biomaterials. This study using FEM was designed to evaluate the thermal stress behavior of a filler-matrix interface. The results were then compared to those of a previous study obtained by a laser thermoacoustic technique (LTAT). The experimental systems (75/25 Bis-GMA/TEGDMA resin reinforced with 0, 25, 50, and 75 wt% 8-microm silanized/unsilanized BaSiO6) as used in the previous study were modeled in this study. The established finite element models were based on coefficient of thermal expansion (CTE) Mismatch Phenomenon. The mechanical properties of the silane coupling agent, such as elastic modulus and thermal expansion coefficient used in the silanized model, were assumed to have optimal heat flux transfer. A third (imaginary) material was proposed to block the transfer of thermal stress between the filler and matrix in the unsilanized model. The thermal load simulation was based on steady-state thermal analysis. The results showed that: (1) The strain energy and interfacial shearing stress calculated from FEM validate the results from the previous LTAT study. (2) Comparing the stress distribution of silanized and unsilanized FEM models, the acoustic signals in LTAT study are mainly derived from debonding of the filler-matrix interface of silanized specimens, and from the matrix area of unsilanized specimens. Based on results to date, we conclude that the finite element method may be a powerful tool for exploring thermoacoustic mechanisms of dental composites.

Suppression of the TPA-induced expression of nuclear-protooncogenes in mouse epidermis by crocetin via antioxidant activity

Crocetin, a major component of the fruit of Gardenia jasminoides Ellis, was investigated for its antitumor promoting effect on 12-O-tetradecanoylphorbol-13-acetate-promoted mouse skin carcinogenesis. Topical application of 5 nmol TPA to CD-1 mice once daily for 5 days caused epidermal hyperplasia, and increases in the levels of c-Fos, c-Jun and c-Myc in the suprabasal layer of epidermis and the muscle layer of dermis. Immunocytolochemical examination showed that pretreatment of 1 mumol crocetin repressed the TPA-induced epidermal hyperplasia and the expressions of c-Jun, c-Fos and c-Myc to the extent of 47, 44 and 45% respectively. Crocetin of 3.0 mumol exhibited stronger inhibition on the induced hyperplasia and the oncoproteins levels (by 60, 53 and 55% respectively). Western blotting analysis confirmed this inhibitory effect of crocetin. Pretreatment of crocetin also repressed the TPA-induced H2O2 production and myeloperoxidase activity. These data indicate that crocetin suppresses the TPA-induced skin carcinogenesis maybe via its antioxidant property which, in turn, leads to a reduction in the TPA-induced expressions of c-Jun, c-Fos and c-Myc in mouse epidermis.

Role of fibronectin deposition in cystogenesis of Madin-Darby canine kidney cells

BACKGROUND

Madin-Darby canine kidney (MDCK) cells cultured within collagen I gel exhibit clonal growth and form spherical multicellular cysts. The cyst-lining epithelial cells are polarized with the basolateral surface in contact with the collagen gel and the apical surface facing the lumen. To understand whether MDCK cysts construct the basal lamina, we characterized the composition of the extracellular matrix deposited by MDCK cysts. The cyst-lining cells produced an apparently incomplete basal lamina containing a discontinuous laminin substratum. In addition, the basal cell surface of the cyst was surrounded by a thick layer of fibronectin. This study was conducted to delineate the role of fibronectin deposition in cystogenesis.

METHODS

MDCK cells cultured in collagen gel were employed. We first used Arg-Gly-Asp (RGD) peptides containing disintegrin rhodostomin to disturb the interaction between fibronectin and the cell surface integrin. We then established several stable transfectants expressing the fibronectin antisense RNA and with which to directly examine the role of fibronectin in cystogenesis.

RESULTS

Rhodostomin markedly decreased the growth rates of the MDCK cyst, suggesting the importance of a normal interaction between fibronectin and integrins. The stable transfectants overexpressing the fibronectin antisense RNA exhibited relatively lower levels of fibronectin and markedly lower cyst growth rates than the control clone. The lower growth rate was correlated with an increase in collagen gel-induced apoptosis.

CONCLUSIONS

The results indicate that the deposition of fibronectin underlying the cyst-lining epithelium serves to prevent apoptosis induced by three-dimensional collagen gel cultures, and hence facilitates cyst growth of MDCK cells.