Intraperitoneal administration of CDP-choline or a combination of cytidine plus choline improves nerve regeneration and functional recovery in a rat model of sciatic nerve injury.

OBJECTIVE: Topical cytidine-5'-diphosphocholine (CDP-choline) improves functional recovery and promotes nerve regeneration in sciatic nerve injury in rats. The aims of this study were to test whether systemic treatment with CDP-choline was effective in improving the recovery of injured sciatic nerve, and to determine whether the cytidine and/or choline moieties of CDP-choline contribute to its beneficial actions. METHODS: Seventy Sprague-Dawley rats underwent a surgical procedure that involved transectioning and immediate surgical repairing of the right sciatic nerve. Rats were assigned to one of five groups and administered intraperitoneally 1 ml/kg of saline (control) or saline containing 600 µmol/kg of each of CDP-choline, cytidine, choline, or cytidine+choline. RESULTS: Recovery in sciatic function index score was greater in rats treated with CDP-choline, choline, or cytidine+choline at 8 and 12 weeks after the interventions. Peripheral nerve regeneration evaluated by electromyography at 12 weeks was also greater in rats receiving CDP-choline (228% of control), choline (168% of control), or cytidine+choline (221% of control). Axon counts and axon density increased significantly following CDP-choline, choline, or cytidine+choline, respectively. Treatment with equivalent dose of cytidine failed to affect sciatic function index, electromyography, and axon counts. Treatment with CDP-choline, but not its metabolites improved nerve adherence and separability score. CONCLUSION: These data show that intraperitoneal CDP-choline, as well as the combination of its metabolites, cytidine+choline, improves functional recovery and promotes regeneration of injured sciatic nerves in rats. CDP-choline also improves nerve adherence and separability.

Alterations in the brain electrical activity in a rat model of sepsis-associated encephalopathy.

Sepsis and septic shock are the commonest causes of death in the intensive care units. Although recent research have improved our understanding of the progress and pathophysiology of sepsis and septic shock, underlying mechanisms in sepsis-associated encephalopathy is still poorly understood. The incidence of sepsis-associated encephalopathy has been reported to vary from 8% to 70% of septic patients. We aimed at investigating the brain's electrical activity using somatosensory-evoked potentials and electrocorticographical recordings in cecal ligation and puncture rat model of sepsis. Significant decrease in mean arterial pressure, increase in heart rate, deteriorated neurological reflexes together with positive blood cultures results, thrombocytopenia and increased blood lactate levels suggesting the successful induction of sepsis in the present study. Elongated latencies and increased amplitudes were observed in somatosensory recordings of septic group, while electrocorticograms revealed slight decrease in median and spectral edge frequencies amplitudes and significantly increased delta activities in 50% of the septic rats. These results would suggest that the studies based on the investigation of the sepsis-associated encephalopathy in animal models needs to be combined with the electrophysiological confirmations of the brain dysfunction following the induction of sepsis.

Morphometric investigation of neurons in the hippocampal CA1, CA3 areas and dentate gyrus in a rat model of sepsis / Investigación morfométrica de neuronas en las áreas hipocampales CA1, CA3 y giro dentado en un modelo de sepsis en rata

Approximately, half of the patients with progressive sepsis develop encephalopathy, but there is scarce knowledge onto question that how the sepsis associated encephalopathy contributes brain dysfunction. Hippocampus is one of the most vulnerable regions during experimental sepsis. In the present study, effects of sepsis on the neuronal density and morphology in CA1, CA3 and DG areas were investigated in a rat model of intraperitoneal sepsis. Twenty-four Wistar rats were divided into three different groups: faecal peritonitis group, sham-operated and un-operated control groups. Pyramidal neuron volume density was significantly higher in CA1 area of the faecal peritonitis group compared to both un-operated (p<0.05) and sham-operated (p<0.05) groups. Pyramidal neuron volume density was also significantly higher in CA3 area of the faecal peritonitis group compared to both un-operated (p<0.05) and sham-operated (p<0.05) groups. Mean nuclear diameter of pyramidal neurons in CA1 area of the faecal peritonitis group was significantly lower (p<0.05) compared to un-operated control group. Dark, shrunken neurons were frequently observed and neuroglial cells appeared to be prevalent in the faecal peritonitis group compared to control groups. These results collectively suggest that intraperitoneal sepsis does not initiate cell death in the early stages of sepsis, although morphological signs of neurodegeneration start to appear.

Aproximadamente, la mitad de los pacientes con sepsis progresiva desarrollan encefalopatía, pero hay escaso conocimiento en cuestión de como la sepsis asociada con encefalopatía contribuye a la disfunción cerebral. El hipocampo es una de las regiones más vulnerables durante la sepsis experimental. En el presente estudio, fueron analizados los efectos de la sepsis sobre la densidad neuronal y la morfología en las áreas CA1, CA3 y giro dentado en un modelo de sepsis intraperitoneal en rata. Veinticuatro ratas Wistar se dividieron en tres grupos diferentes: grupo de peritonitis fecal, operación simulada y control no operado. La densidad del volúmen piramidal fue significativamente mayor en el área CA1 del grupo con peritonitis fecal en comparación con los grupos no operados (p<0,05) y la operación simulada (p<0,05). La densidad de volumen de las neuronas piramidales fue significativamente mayor en el área CA3 del grupo peritonitis fecal en comparación con los no operado (p<0,05) y la operación simulada (p<0,05). El diámetro promedio nuclear de las neuronas piramidales en la zona CA1 del grupo de peritonitis fecal fue significativamente menor (p<0,05) en comparación con el grupo de control no operado. Las neuronas fueron observadas con frecuencia reducidas y las células neurogliales parecen ser frecuentes en el grupo de peritonitis fecal en comparación con grupos de control. Estos resultados en conjunto sugieren que la sepsis intraperitoneal no inicia la muerte celular en las primeras etapas de la sepsis, aunque los signos morfológicos de la neurodegeneración empiezan a aparecer.

Use of an intact sensory nerve to bridge a motor nerve defect: an experimental study.

OBJECT: End-to-side neurorrhaphy has recently became popular for peripheral nerve repair. Although this method is mainly indicated in nerve defects in which there is an absent proximal nerve stump, bridging a motor nerve defect by coapting the proximal and distal ends of the defect to a neighboring mixed nerve in an end-to-side fashion has been another experimental use of this method. In this situation, however, the source of the regenerating axons is unclear because the axons in both the proximal end of the defect and the bridging intact nerve have the capacity for regeneration. The goal of this study was to identify the source of the regenerating axons. METHODS: In this experimental study, the authors used a sensory nerve to bridge a motor nerve defect so that they could elucidate the source of the regenerating motor axons in the distal part of the motor nerve. One advantage of using a sensory nerve was that it eradicated the risk of damaging another motor nerve. Tests used in the analysis included gait evaluation, electrophysiological tests, and histological assessment. CONCLUSIONS: Results of this study showed that, in the rat model, a sensory nerve can be used to bridge a motor nerve defect, thereby eliminating the need for nerve grafting.

Simultaneous end-to-side coaptations of two severed nerves to a single healthy nerve in rats.

OBJECT: This experimental study was designed to evaluate functional and sensory outcomes and morphological features observed after simultaneous end-to-side coaptations of distal stumps of two nerves to a single neighboring nerve. Studies were performed using both parallel and end-to-side coaptation (PEC) and serial end-to-side coaptation (SEC) methods in a rat model. METHODS: In the PEC group, distal stumps of the sural and common fibular nerves were coapted to the intact tibial nerve 1 cm apart from each other in an end-to-side fashion. In the SEC group, identical surgical procedures apart from the coaptation method were conducted. For the coaptation method in this group, the distal stump of the common fibular nerve was first coapted to the side of the intact tibial nerve, and then the distal stump of the sural nerve was coapted to the side of the common fibular nerve 1 cm apart from the first coaptation site. Nonoperated contralateral sides were used as controls. Nerve regeneration in both groups was evaluated functionally, electrophysiologically, and histomorphometrically. CONCLUSIONS: When there is a need for two end-to-side coaptations of two severed nerves, PEC is the recommended method of choice to obtain better axonal regeneration into both nerves.

Perimicrovascular edema in the frontal cortex in a rat model of intraperitoneal sepsis.

Septic encephalopathy is a complication of sepsis, and it is closely associated with the increased mortality of the sufferers. Pathophysiology of septic encephalopathy is not still completely understood. In an attempt to provide insight into the pathogenesis of septic encephalopathy, a light and electron microscopic investigation has been carried out in a rat model of intraperitoneal sepsis. Experimental fecal peritonitis was induced in Wistar rats which have been monitored for 6 h and sacrificed to harvest the samples of frontal cortex. Vital parameters and morphometric data obtained from investigation of the microvessels were then compared with the sham-operated and unoperated controls. In addition to the discernible drop in the blood pressure and in rectal temperature following initial increases, unstable but usually increased heart rate and marked respiratory failure were recorded. Estimation of the percentage of the microvessel area occupied by edema revealed the presence of significantly more perimicrovascular edema in the experimental fecal peritonitis group compared to both sham-operated and unoperated controls, while no significant difference was present between the latter two groups. Electron microscopic investigation confirmed the presence of distinctive perimicrovascular edema in the fecal peritonitis group although the endothelial cells were linked by tight junctions which appeared morphologically intact. Although it might be premature to draw any strict parallels between the septic encephalopathy in humans and the findings observed in the present model, the results may suggest that the edema observed around the microvessels would bare a role in the pathogenesis of the septic encephalopathy probably by affecting the exchange of oxygen and nutrients with carbon dioxide and waste products between the blood and brain parenchyma.

End-to-side nerve coaptation: is an additional proximal coaptation useful when available?

The aim of this experimental study was to evaluate the effects of end-to-side coaptation of the proximal end of a severed nerve to the same intact nerve, in addition to traditional end-to-side coaptation of the distal end, with an aim to use the intact nerve as a nerve conduit in a rat model and to compare the functional and histologic results of this modality to those obtained after nerve grafting and traditional end-to-side nerve coaptation. In group A, a peroneal nerve defect measuring 1 cm was created in the left hind limb, and a nerve graft 1 cm long was used to bridge the defect. In group B, only the distal stump of the peroneal nerve was coapted to the intact tibial nerve. In group C, both ends of the peroneal nerve defect were coapted to the intact tibial nerve in an end-to-side fashion 1.5 cm apart from each other, and in group D, the peroneal nerve defect was left unrepaired. Group E was consisted of nonoperated peroneal nerves that were used to obtain normative data. Although significantly higher myelinated axon densities were observed in groups B and C compared with group A and group E, total number of the myelinated axons was significantly higher only in group C. Peroneal functional index assessments demonstrated that nerve recovery in the peroneal nerve was similar in groups A and C, and both were better than those observed in groups B and D. Collectively, these results suggest that end-to-side coaptation of both ends of a severed nerve to an intact nerve, in case of a nerve defect in this length, may serve as an alternative for nerve grafting.

Deficits of neuronal density in CA1 and synaptic density in the dentate gyrus, CA3 and CA1, in a mouse model of Down syndrome.

Ts65Dn mice are partially trisomic for the distal region of MMU16, which is homologous with the obligate segment of HSA21 triplicated in Down syndrome (DS). Ts65Dn mice are impaired in learning tasks that require an intact hippocampus. In order to investigate the neural basis of these deficits in this mouse model of Down syndrome, quantitative light and electron microscopy were used to compare the volume densities of neurons and synapses in the hippocampus of adult Ts65Dn (n=4) and diploid mice (n=4). Neuron density was significantly lower in the CA1 of Ts65Dn compared to diploid mice (p<0.01). Total synapse density was significantly lower in the dentate gyrus (DG; p<0.001), CA3 (p<0.05) and CA1 (p<0.001) of Ts65Dn compared to diploid mice. The synapse-to-neuron ratio was significantly lower in the DG (p<0.001), CA3 (p<0.01) and CA1 (p<0.001) of Ts65Dn compared to diploid mice. When the data were broken down by synapse type, asymmetric synapse density was found to be significantly lower in the DG (p<0.001), CA3 (p<0.05) and CA1 (p<0.001) of Ts65Dn compared to diploid mice, while such a difference in symmetric synapse density was only present in the DG (p<0.01). The asymmetric synapse-to-neuron ratio was significantly lower in the DG (p<0.001), CA3 (p<0.01) and CA1 (p<0.001) of Ts65Dn compared to diploid mice, but there were no such significant differences in symmetric synapse-to-neuron ratios. These results suggest that impaired synaptic connectivity in the hippocampus of Ts65Dn mice underlies, at least in part, their cognitive impairment.