Distinct Mechanoresponsive Luminescence, Thermochromism, Vapochromism, and Chlorine Gas Sensing by a Solid-State Organic Emitter.

In this study, we report a synthetically simple donor-acceptor (D-A)-type organic solid-state emitter 1 that displays unique fluorescence switching under mechanical stimuli. Orange and yellow emissive crystals of 1 (1O, 1Y) exhibit an unusual "back and forth" fluorescence response to mechanical force. Gentle crushing (mild pressure) of the orange or yellow emissive crystal results in hypsochromic shift to cyan emissive fragments (λem = 498-501 nm) with a large wavelength shift Δλem = -71 to -96 nm, while further grinding results in bathochromic swing to green emissive powder λem = 540-550 nm, Δλem = +40 to 58 nm. Single-crystal X-ray diffraction study reveals that molecules are packed by weak interactions, such as C-H···π, C-H···N, and C-H···F, which facilitate intermolecular charge transfer in the crystal. With the aid of structural, spectroscopic, and morphological studies, we established the interplay between intermolecular and intramolecular charge-transfer interaction that is responsible for this elusive mechanochromic luminescence. Moreover, we have also demonstrated the application of this organic material for chlorine gas sensing in solid state.

Learning and cognitive deficits in hypoxic neonatal rats intensified by BAX mediated apoptosis: protective role of glucose, oxygen, and epinephrine.

Hypoxic brain injury during neonatal development can lead to neuronal damage and produce learning and cognitive impairments. TOPRO-3 staining was used to visualize cell loss and real-time polymerase chain reaction (PCR) analysis of BAX mRNA was used to evaluate the level of apoptosis in the cerebral cortex, cerebellum, brain stem, and striatum of hypoxic neonatal rats and hypoxic rats resuscitated with glucose, oxygen, and epinephrine. The long-term effects of neonatal hypoxic insult on cognition and behavior were studied using Morris water maze experiment on 1-month-old rats exposed to neonatal hypoxia. In hypoxic neonatal rats, a significant cell loss (p < .001) within the brain regions was observed in TOPRO-3 staining and BAX mRNA expression was significantly upregulated (p < .001). Immediate resuscitation of hypoxic neonates with glucose, alone and along with oxygen, significantly downregulated (p < .001) BAX mRNA expression. The BAX expression in epinephrine resuscitated and 100% oxygen resuscitated groups were found to be upregulated in the brain regions. In water maze experiment, 1-month-old rats exposed to neonatal hypoxia spent lesser time in the platform quadrant (p < .001) and showed longer escape latency (p < .001) highlighting the learning and cognitive deficits. Our study revealed the effect of glucose resuscitation alone and along with oxygenation in ameliorating the spatial memory and learning deficits induced by neonatal hypoxic insult mediated brain cell loss.

Cholinergic receptor alterations in the brain stem of spinal cord injured rats.

Cholinergic receptors in upper motor neurons of brain stem control locomotion and coordination. Present study unravels cholinergic alterations in brain stem during spinal cord injury to understand signalling pathway changes which may be associated with spinal cord injury mediated motor deficits. We evaluated cholinergic function in brain stem by studying the expression of choline acetyl transferase and acetylcholine esterase. We quantified metabotropic muscarinic cholinergic receptors by receptor assays for total muscarinic, muscarinic M1 and M3 receptor subunits, gene expression studies using Real Time PCR and confocal imaging using FITC tagged secondary antibodies. The gene expression of ionotropic nicotinic cholinergic receptors and confocal imaging were also studied. The results from our study showed metabolic disturbance in cholinergic pathway as choline acetyl transferase is down regulated and acetylcholine esterase is up regulated in spinal cord injury group. The significant decrease in muscarinic receptors showed by decreased receptor number along with down regulated gene expression and confocal imaging accounts for dysfunction of metabotropic acetylcholine receptors in spinal cord injury group. Ionotropic acetylcholine receptor alterations were evident from the decreased gene expression of alpha 7 nicotinic acetylcholine receptors and confocal imaging. The motor coordination was analysed by Grid walk test which showed an increased foot slips in spinal cord injured rats. The significant reduction in brain stem cholinergic function might have intensified the motor dysfunction and locomotor disabilities.