Biology subjects

Netam, R.

Publications and source records attributed to Netam, R..

2 recordsLinked to original sources

bioRxiv2022

Effect of 15 days hindlimb unloading on baroreflex sensitivity, Hear rate variability and Carotid artery structure in rats

IntroductionIn space, cephalad shift of body fluid equalizes the blood pressure throughout the body leading to various cardiovascular disturbances in space and upon return on earth. Effects of microgravity on humans can be simulated on earth by hindlimb unloading (HU) rat models l. This study was planned to examine the Effect of 15 days hindlimb unloading on baroreflex sensitivity, Herat rate variability (HRV) and carotid artery structure in rats. Material and methods18 male Wistar rats weighing 250-300 gm were randomly divided into control and hindlimb unloading groups and housed in separate cages for 15 days. Body weight, food and water intake was measured every day. The pelvic suspension method was used to simulate effects of microgravity. To record HRV, ECG was recorded in lead II configuration on the 15th day. Then blood pressure was recorded directly from the carotid artery. Linear regression of arterial pressure and RR interval used to derive the Baroreflex sensitivity. Vessel wall thickness, intimal thickness, smooth muscle cell layer thickness & luminal diameter were compared after H&E staining. Ultrathin sectioning and counter-staining was done for electron microscopy and Changes in endothelial thickness, elastic lamina, and deeper artery structures were observed. Statistical analysis was done using Graphpad Prism (version 9.0). Unpaired t-test, Mann Whitney and 2 way ANOVA were used according to groups and distribution of parameters. ResultsWe found significant differences in Food intake (p {square}0.001), Body weight (p {square}0.001), Heart rate (p=0.031), BRS (p= 0.026), R-R interval (p=0.0246), heart rate variability parameters {SDSD (p=0.0001), RMSD (p= 0.0001), VLF(p=0.001),HF (p=0.0054), LF/HF Ratio (p= 0.0001)}. We did not found significant changes in Water intake, MAP, SBP, DBP, Vessel wall thickness, Luminal Diameter, Intimal thickness, Smooth muscle thickness, in H&E staining and in electron microscopy. ConclusionChronic microgravity simulation using pelvic suspension showed a decrease in BRS after 15 days of HU; however 15 days of HU was not insufficient to produce any structural changes in the carotid artery. BRS changes were accompanied by change in vascular vasoconstriction and vasodilation properties which were due to alteration in the sympathetic and parasympathetic outflow.

physiology↗

bioRxiv2022

Acute sleep deprivation induces synaptic remodeling at the soleus muscle neuromuscular junction in rats

Sleep is important for cognitive and physical performance. Sleep deprivation not only affects neural functions but also results in muscular fatigue. A good nights sleep reverses these functional derangements caused by sleep deprivation. The role of sleep in brain function has been extensively studied. However, its role in neuromuscular junction or skeletal muscle morphology is sparsely addressed although skeletal muscle atonia and suspended thermoregulation during rapid eye movement sleep possibly provides a conducive environment for the muscle to rest and repair; somewhat similar to slow-wave sleep for synaptic downscaling. In the present study, we have investigated the effect of 24 h sleep deprivation on the neuromuscular junction morphology and neurochemistry using electron microscopy and immunohistochemistry in the rat soleus muscle. Acute sleep deprivation altered synaptic ultra-structure viz. mitochondria, synaptic vesicle, synaptic proteins, basal lamina, and junctional folds needed for neuromuscular transmission. Further acute sleep deprivation showed the depletion of the neurotransmitter acetylcholine and the overactivity of its degrading enzyme acetylcholine esterase at the neuromuscular junction. The impact of sleep deprivation on synaptic homeostasis in the brain has been extensively reported recently. The present evidence from our studies shows new information on the role of sleep on neuromuscular junction homeostasis and its functioning. Statement of significanceSleep causes synaptic downscaling in the brain, and allows the brain to carry out various housekeeping functions. Here we have reported that the function of the sleep-wake cycle on the synaptic homeostasis extends beyond the brain. Acute sleep deprivation caused significant alteration at ultra and macrostructure of antigravity muscle and the neuromuscular junction along with adaptation to new fiber type in rats. These morpho-functional changes were well correlated with the biochemical assessment of the acetylcholine at the neuromuscular junction. These changes were partially recovered when the rats were allowed to recover from sleep deprivation. The findings suggest a new avenue for a sleep study; employing the neuromuscular junction for exploring the effect of sleep at energy and synaptic homeostasis levels.

neuroscience↗