Versatile Room-Temperature-Phosphorescent Materials Prepared from N-Substituted Naphthalimides: Emission Enhancement and Chemical Conjugation

Purely organic materials with room-temperature phosphorescence (RTP) are currently under intense investigation because of their potential applications in sensing, imaging, and displaying. Inspired by certain organometallic systems, where ligand-localized phosphorescence ((3) π-π*) is mediated by ligand-to-metal or metal-to-ligand charge transfer (CT) states, we now show that donor-to-acceptor CT states from the same organic molecule can also mediate π-localized RTP. In the model system of N-substituted naphthalimides (NNIs), the relatively large energy gap between the NNI-localized (1) π-π* and (3) π-π* states of the aromatic ring can be bridged by intramolecular CT states when the NNI is chemically modified with an electron donor. These NNI-based RTP materials can be easily conjugated to both synthetic and natural macromolecules, which can be used for RTP microscopy.

Hydroxysafflor Yellow A Protects Neurons From Excitotoxic Death through Inhibition of NMDARs

Excessive glutamate release causes overactivation of N-methyl d-aspartate receptors (NMDARs), leading to excitatory neuronal damage in cerebral ischemia. Hydroxysafflor yellow A (HSYA), a compound extracted from Carthamus tinctorius L., has been reported to exert a neuroprotective effect in many pathological conditions, including brain ischemia. However, the underlying mechanism of HSYA's effect on neurons remains elusive. In the present study, we conducted experiments using patch-clamp recording of mouse hippocampal slices. In addition, we performed Ca²⁺ imaging, Western blots, as well as mitochondrial-targeted circularly permuted yellow fluorescent protein transfection into cultured hippocampal neurons in order to decipher the physiological mechanism underlying HSYA's neuroprotective effect.

Through the electrophysiology experiments, we found that HSYA inhibited NMDAR-mediated excitatory postsynaptic currents without affecting α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor and γ-aminobutyric acid A-type receptor-mediated currents. This inhibitory effect of HSYA on NMDARs was concentration dependent. HSYA did not show any preferential inhibition of either N-methyl d-aspartate receptor subtype 2A- or N-methyl d-aspartate receptor subtype 2B- subunit-containing NMDARs. Additionally, HSYA exhibits a facilitatory effect on paired NMDAR-mediated excitatory postsynaptic currents. Furthermore, HSYA reduced the magnitude of NMDAR-mediated membrane depolarization currents evoked by oxygen-glucose deprivation, and suppressed oxygen-glucose deprivation–induced and NMDAR-dependent ischemic long-term potentiation, which is believed to cause severe reperfusion damage after ischemia. Through the molecular biology experiments, we found that HSYA inhibited the NMDA-induced and NMDAR-mediated intracellular Ca²⁺ concentration increase in hippocampal cultures, reduced apoptotic and necrotic cell deaths, and prevented mitochondrial damage. Together, our data demonstrate for the first time that HSYA protects hippocampal neurons from excitotoxic damage through the inhibition of NMDARs. This novel finding indicates that HSYA may be a promising pharmacological candidate for the treatment of brain ischemia.

Progranulin and short-term outcome in patients with acute ischaemic stroke

BACKGROUND AND PURPOSE

Stroke is a leading cause of death and severe disability worldwide. Serum biomarkers play a critical role in the assessment of the severity and prognosis in stroke patients.

METHODS

In this prospective cohort study, the measurement of serum progranulin (PGRN) was conducted in 316 participants, including 216 patients with an identified diagnosis of acute ischaemic stroke and 100 normal control subjects. The primary end-point was defined as all-cause mortality for a short-term follow-up of 6 months. Adverse functional outcome (modified Rankin Scale score ≥3) was considered as the secondary end-point.

RESULTS

The median value of serum PGRN for patients with acute ischaemic stroke was 64.2 ng/ml (interquartile range 54.6-73.7), which was significantly higher than the control group [59.7 (54.4-64.4) ng/ml; P < 0.001]. Multivariable linear regression suggested that PGRN levels were significantly correlated with body mass index, alcohol consumption, fasting blood glucose, total cholesterol, National Institutes of Health Stroke Scale (NIHSS) score and high-density lipoprotein cholesterol. Serum PGRN concentrations were independently associated with increased risks of all-cause mortality and adverse functional outcome after adjustment for clinical variables. In Cox proportional hazards models, PGRN levels were associated with the risk of mortality (hazard ratio 1.090, 95% confidence interval 1.033-1.150, P = 0.002). The net reclassification improvement of the model with added PGRN was 0.1902 (P = 0.0234) after adjustment for the variables in the Cox regression model for predicting all-cause mortality, and the integrated discrimination improvement was 0.1052 (P < 0.001).

CONCLUSIONS

Serum PGRN levels independently predicted all-cause mortality and adverse functional outcome in the short term in stroke patients. The discriminative power was improved by PGRN on the basis of NIHSS score.

Direct detection of optogenetically evoked oscillatory neuronal electrical activity in rats using SLOE sequence

The direct detection of neuronal electrical activity is one of the most challenging goals in non-BOLD fMRI research. Previous work has demonstrated its feasibility in phantom and cell culture studies, but attempts in in vivo studies remain few and far between. Most recent in vivo studies used T2*-weighted sequences to directly detect neuronal electrical activity evoked by sensory stimulus. As neuronal electrical signal is usually comprised of a series of spectrally distributed oscillatory waveforms rather than being a direct current, it is most likely to be detected using oscillatory current sensitive sequences. In this study, we explored the potential of using the spin-lock oscillatory excitation (SLOE) sequence with spiral readout to directly detect optogenetically evoked oscillatory neuronal electrical activity, whose main spectral component can be manipulated artificially to match the resonance frequency of spin-lock RF field. In addition, experiments using the stimulus-induced rotary saturation (SIRS) sequence with spiral readout were also performed. Electrophysiological recording and MRI data acquisition were conducted on separate animals. Robust optogenetically evoked oscillatory LFP signals were observed and significant BOLD signals were acquired with the GE-EPI sequence before and after the whole SLOE and SIRS acquisitions, but no significant neuronal current MRI (ncMRI) signal changes were detected. These results indicate that the sensitivity of oscillatory current sensitive sequences needs to be further improved for direct detection of neuronal electrical activity.

Cryo-EM structure of the mature dengue virus at 3.5-Å resolution

Regulated by pH, membrane-anchored proteins E and M play a series of roles during dengue virus maturation and membrane fusion. Our atomic model of the whole virion from cryo electron microscopy at 3.5Å resolution reveals that in the mature virus at neutral extracellular pH, the N-terminal 20-amino acid segment of M (involving three pH-sensing histidines) latches and thereby prevents spring-loaded E fusion protein from prematurely exposing its fusion peptide. This M latch was fastened at an earlier stage, during maturation at acid pH in the trans-Golgi network. At a later stage, to initiate infection in response to acid pH in the late endosome, M releases the latch and exposes the fusion peptide. Thus, M serves as a multistep chaperone of E to control the conformational changes accompanying maturation and infection. These pH-sensitive interactions could serve as targets for drug discovery.

Ultrastructural analysis of neuronal synapses using state-of-the-art nano-imaging techniques

Neuronal synapses are functional nodes in neural circuits. Their organization and activity define an individual's level of intelligence, emotional state and mental health. Changes in the structure and efficacy of synapses are the biological basis of learning and memory. However, investigation of the molecular architecture of synapses has been impeded by the lack of efficient techniques with sufficient resolution. Recent developments in state-of-the-art nano-imaging techniques have opened up a new window for dissecting the molecular organization of neuronal synapses with unprecedented resolution. Here, we review recent technological advances in nano-imaging techniques as well as their applications to the study of synapses, emphasizing super-resolution light microscopy and 3-dimensional electron tomography.

Differences in Growth, and Nitrogen Uptake and Storage Between Two Container-Grown Cultivars of Rhododendron

One-year-old liners of an evergreen rhododendron (Rhododendron L. ‘H-1 P.J.M’) and a deciduous azalea (Rhododendron L. ‘Cannon's Double’) were used to determine nitrogen (N) uptake, remobilization, and storage in relation to plant growth from May to September. Plants were grown in a substrate of equal parts (by vol) vermiculite, pumice, and sandy loam soil and received liquid fertilization with or without N. Rate of N uptake was correlated with the rate of plant growth and maximum uptake occurred during July [azalea, &gt;4 mg/day (1.4E – 04 oz/day)] and August [rhododendron, &gt;2 mg/day (7.1E – 05 oz/day)]. Compared to the rhododendron used in this study, the azalea cultivar grew faster and had a greater rate of N uptake and uptake efficiency (azalea, 12 to 33%; rhododendron, 8 to 16%). The old leaves of the rhododendron remobilized N for new growth. New azalea leaves exported approx. 40% of their N by September when the stems and roots were actively accumulating biomass. The roots, stems and new leaves of the rhododendrons were still accumulating biomass by September. Our results suggest that transplanted 1-year-old liners of rhododendron and azalea contained sufficient N reserves in both the plant and substrate to support initial plant growth and that increasing availability of N in the substrate during the period of rapid growth can significantly increase N uptake while improving vegetative growth and the N status of both rhododendron and azalea.

Expression of testis specific ankyrin repeat and SOCS box-containing 17 gene

Human ASB-17 (Ankyrin Repeat and SOCS Box-containing 17) is a recently identified gene belonging to the ASB family, isolated from testis cDNA library. Human ASB-17 is expressed exclusively in testis among 16 tissues, revealed by Northern blot. Mouse Asb-17 was shown to be expressed from the third week post birth to adult by semi-quantitative RT-PCR analysis. In situ hybridization on frozen sections demonstrated that Asb-17 is expressed in spermatogenic cells in adult mouse, but not in Leydig cell and epididymis in adult mouse. ASB-17 proteins are highly conserved in mammals including human, mouse, rat, Canis familiaris and Macaca fascicularis.

Selective presynaptic propagation of long-term potentiation in defined neural networks

Induction of long-term potentiation (LTP) of the synaptic connection between two hippocampal glutamatergic neurons in a neural network formed in cell culture resulted in a specific pattern of potentiation at other connections within the network. We found that potentiation propagated from the site of induction retrogradely to glutamatergic or GABAergic synapses received by the dendrites of the presynaptic neuron and laterally to those made by its axonal collaterals onto other glutamatergic cells. In contrast, synapses made by the same presynaptic neuron onto GABAergic cells were not affected, and there was no postsynaptic lateral or forward propagation to other synapses received or made by the postsynaptic neuron. In addition, there was no secondary propagation to synapses not directly associated with the presynaptic neuron. Both induction and propagation of LTP required correlated spiking of the postsynaptic cell as well as the activation of the NMDA subtype of glutamate receptors. Such selective propagation suggests the existence of a long-range cytoplasmic signaling within the presynaptic neuron, leading to a specific pattern of coordinated potentiation along excitatory pathways in a neural network.

[Germline LKB1 gene mutation screening in 4 Chinese Peutz-Jeghers syndrome pedigrees]

OBJECTIVE

To evaluate the frequency and nature of LKB1 gene germline mutations in 4 large Chinese Peutz-Jeghers syndrome pedigrees.

METHODS

Four Chinese Peutz-Jeghers syndrome pedigrees were investigated. Two patients and 1 normal adult from each pedigree were selected, and genomic DNA from peripheral blood was extracted. The 9 exons of LKB1 gene were amplified by PCR. The products were tested by SSCP and abnormally shifted bands were sequenced. If there was no positive finding in any pedigree, the entire exons were sequenced.

RESULTS

The same 842 C deletion of LKB1 gene frame-shift mutations was found in 2 pedigrees, which resulted in truncated protein. No exon variant was found in the left 2 pedigrees.

CONCLUSIONS

LKB1 gene germline mutation is an important molecular pathogen of Peutz-Jeghers syndrome. 842 C deletion is a possible mutation hotspot and might be a common-ancestor mutation characteristic of Chinese.

[The rapid effects of steroids on glycine uptake in neuroblastoma cell strain SK-N-SH cells]

In the present study, glycine uptake in SK-N-SH cells was determined with liquid scintillation technique, and the rapid effects of steroids on glycine uptake in SK-N-SH cells were investigated. The results were as follows. High-affinity glycine uptake in SK-N-SH cells was dependent on Na+ and Cl-. Corticosterone (CORT), progesterone (P) and dexamethasone (DEX) had rapid effects on the glycine uptake. Since estradiol (E2) and deoxycorticosterone (DOC) had no effects, it was suggested that the rapid effects of steroids were specific. The rapid effects of CORT were concentration-dependent in a range of 10(-9)-10(-6) mol/L. The rapid effects were not affected by the inhibitor of protein synthesis and persisted even when CORT was conjugated with bovine serum album, but attenuated when Ca2+ was absent in the external medium. The results suggest that the steroid effect on glycine uptake in SK-N-SH cells was nongenomicly mediated.

Distributed synaptic modification in neural networks induced by patterned stimulation

Activity-dependent changes in synaptic efficacy or connectivity are critical for the development, signal processing and learning and memory functions of the nervous system. Repetitive correlated spiking of pre- and postsynaptic neurons can induce a persistent increase or decrease in synaptic strength, depending on the timing of the pre- and postsynaptic excitation. Previous studies on such synaptic modifications have focused on synapses made by the stimulated neuron. Here we examine, in networks of cultured hippocampal neurons, whether and how localized stimulation can modify synapses that are remote from the stimulated neuron. We found that repetitive paired-pulse stimulation of a single neuron for brief periods induces persistent strengthening or weakening of specific polysynaptic pathways in a manner that depends on the interpulse interval. These changes can be accounted for by correlated pre- and postsynaptic excitation at distant synaptic sites, resulting from different transmission delays along separate pathways. Thus, through such a 'delay-line' mechanism, temporal information coded in the timing of individual spikes can be converted into and stored as spatially distributed patterns of persistent synaptic modifications in a neural network.

Triplex formation by oligonucleotides containing novel deoxycytidine derivatives

Homopurine sequences of duplex DNA are binding sites for triplex-forming oligodeoxyribopyrimidines. The interactions of synthetic duplex DNA targets with an oligodeoxyribopyrimidine containing N4-(6-amino-2-pyridinyl)deoxycytidine (1), a nucleoside designed to interact with a single C-G base pair interruption of the purine target tract, was studied by UV melting, circular dichroism spectroscopy and dimethylsulfate alkylation experiments. Nucleoside 1 supports stable triplex formation at pH 7.0 with formation of a 1-Y-Z triad, where Y-Z is a base pair in the homopurine tract of the target. Selective interaction was observed when Y-Z was C-G, although A-T and, to a lesser extent, T-A and G-C base pairs were also recognized. The circular dichroism spectra of the triplex having a 1-C-G triad were similar to those of a triplex having a C(+)-G-C triad, suggesting that the overall structures of the two triplexes are quite similar. Removal of the 6-amino group from 1 essentially eliminated triplex formation. Reaction of a triplex having the 1-C-G triad with dimethylsulfate resulted in a 50% reduction of methylation of the G residue of this triad. In contrast, the G of a similar triplex containing a U-C-G triad was not protected from methylation by dimethylsulfate. These results are consistent with a binding mode in which the 6-amino-2-pyridinyl group of 1 spans the major groove of the target duplex at the 1-C-G binding site and forms a hydrogen bond with the O6 of G. An additional stabilizing hydrogen bond could form between the N4 of the imino tautomer of 1 and the N4 amino group of C.

Triplex formation by a psoralen-conjugated oligodeoxyribonucleotide containing the base analog 8-oxo-adenine

Oligodeoxyribonucleotides containing thymidine and 8-oxo-2'-deoxyadenosine can form pyr.pur.pyr type triplexes with double-stranded DNA. Unlike triplexes whose third strands contain thymidine and deoxycytidine, the stability of these triplexes is independent of pH. We have prepared d-ps-TAAATAAATTTTTAT-L [I(A)], where A is 8-oxo-2'-deoxyadenosine, ps is 4'-hydroxymethyl-4,5',8- trimethylpsoralen and L is a 6-amino-2-(hydroxymethyl)hexyl linker. The oligomer is designed to interact with a homopurine sequence in the promoter region of the human gene coding for the 92 kDa form of collagenase type IV. Oligomer I(A) and oligomer I(C), which contains 2'-deoxycytidine in place of 8-oxo-2'-deoxycytidine, both form stable triplexes at pH 6.2, but only I(A) forms a stable triplex with a model duplex DNA target at pH 7.5, as determined by UV melting experiments. Triplex formation is stabilized by the presence of the psoralen group. Upon irradiation both I(A) and I(C) form photoadducts with the DNA target at pH 6.2, but only I(A) forms a photoadduct at pH 7.5. In these photoreactions oligomer I(A) appears to selectively form a photoadduct with a C in the purine-rich strand of the duplex target. Although a T residue is present in the pyrimidine-rich strand of the target at the duplex/triplex junction, essentially no adduct formation takes place with this strand, nor is interstrand cross-linking observed. The extent of photoadduct formation decreases with increasing temperature, behavior which is consistent with the UV melting curve of the triplex. A tetramethylrhodamine derivative of I(A) was prepared and found to cross-link less extensively than I(A) itself. Oligomer I(A) is completely resistant to hydrolysis when incubated for 24h in the presence of 10% fetal bovine serum at 37 degree C, although it is hydrolyzed by S1 nuclease. The properties of oligomer I(A) suggest that 8-oxo- containing oligomers may find utility as antigene oligonucleotide reagents.