Fabrication and evaluation of microgrooved polymers as peripheral nerve conduits

Cell alignment plays an important role in the repair of damaged peripheral nerves. The aligned Schwann cells could direct the axonal outgrowth during nerve reconstruction. One way of aligning Schwann cells is to use surface grooves in micrometric dimensions. In this study, microgrooves on chitosan or poly(d,l-lactide) (PLA) were fabricated and the behaviors of Schwann cells and glial cell line C6 on these surfaces were examined. It was found that Schwann cells and C6 cells could be successfully aligned by the microgrooves, and express the genes related to the production of neurotrophic factors. The polymer conduits with microgrooves on the inner surface were implanted in rats to repair the damaged sciatic nerve. The microgrooved conduits were demonstrated to enhance peripheral nerve regeneration as compared to the smooth conduits.     

Effect of tetrapeptide cortagen on regeneration of sciatic nerve

Intramuscular injection of 10 μg/kg cortagen to rats during 10 days after transsection and suturing of the sciatic nerve increased the growth rate and conduction velocity in the regenerating nerve fibers by 27% and 40%, respectively. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 130, No. 12, pp. 654–656, December, 2000     

Effects of stanozolol and L-carnitine on erythrocyte osmotic fragility during aerobic exercise in rats

The effect on erythrocyte osmotic fragility of two anabolic agents, widely used to improve physical performance, has been studied. These agents, the steroid derivative, stanozolol, and a quaternary amine,l-carnitine, were administered to rats at rest and while performing running exercises, for 12 weeks. The results show that exercise does not alter the haemolysis curve. Administration of both agents in resting condition does increase the osmotic resistance of the erythrocytes. The combined effect of drug administration and physical exercise further increases the osmotic resistance in the case of stanozolol, presumably due to the steroid-erythrocyte membrane interaction as well as by an erthyropoietic effect.     

The stimulus-secretion coupling of amino acid-induced insulin release

l-Glutamine enhances insulin release evoked byl-leucine in isolated rat pancreatic islets. The enhancing action ofl-glutamine, which is a rapid but steadily increasing and not rapidly reversible phenomenon, is not attributable to any major change in either K⁺ or Ca²⁺ outflow from the islet cells. It coincides with an apparent increase in Ca²⁺ inflow rate and, hence, with Ca accumulation in the islets. The initial ionic response tol-leucine is not qualitatively altered by the presence ofl-glutamine. In their combined capacity to stimulate⁴⁵Ca net uptake in the islets,l-glutamine can be replaced byl-asparagine but not byl-glutamate, whereasl-leucine can be replaced byl-norvaline orl-isoleucine, but not byl-valine, glycine orl-lysine. Such a specificity is identical to that characterizing the effect of these various amino acids upon insulin release. It is postulated that the release of insulin evoked by the combination ofl-leucine andl-glutamine involves essentially the same remodelling of ionic fluxes as that evoked by other nutrient secretagogues with, however, an unusual time course for the functional response tol-glutamine.     

Early nerve ending rescue from oxidative damage and energy failure by <Emphasis Type="SmallCaps">l</Emphasis>-carnitine as post-treatment in two neurotoxic models in rat: recovery of antioxidant and reductive capacities

Cell rescue is a primary need during acute and chronic insults to the central nervous system. Functional preservation during the early stages of toxicity in a given degenerative event may represent a significant amelioration of detrimental processes linked to neuronal cell loss. Excitotoxicity and depleted cellular energy are toxic events leading to cell death in several neurodegenerative disorders. In this work, the effects of the well-known antioxidant and energy precursor, l-carnitine (l-CAR), were tested as a post-treatment in two neurotoxic models under in vitro and in vivo conditions. The experimental models tested included: (1) a typical excitotoxic and pro-oxidant inducer, quinolinic acid (QUIN); and (2) a mitochondrial energy inhibitor, 3-nitropropionic acid (3-NP). For in vitro studies, increasing concentrations of l-CAR (10–1,000 μM) were added to the isolated brain synaptosomes at different times (1, 3 and 6 h) after the incubation with toxins (100 μM QUIN and 1 mM 3-NP), and 30 min later, lipid peroxidation (LP) and mitochondrial dysfunction (MD) were evaluated. For in vivo purposes, l-CAR (100 mg/kg, i.p.) was given to rats either as a single administration 120 min after the intrastriatal infusion of QUIN (240 nmol/μl) or 3-NP (500 nmol/μl), or for 7 consecutive days (starting 120 min post-lesion). LP and MD were evaluated 4 h and 7 days post-lesions in isolated striatal synaptosomes. Our results show that, despite some variations depending on the toxic model tested, the time of exposure, or the biomarker evaluated, nerve ending protection can be mostly achieved by l-CAR within the first hours after the toxic insults started, suggesting that targeting the ongoing oxidative damage and/or energy depletion during the first stages of neurotoxic events is essential to rescue nerve endings. D. Elinos-Calderón and Y. Robledo-Arratia equally contributed to this work.     

Selection of intact fine nerve strands using power spectrum of their electrical noise

Experiments on narcotized cats demonstrated a decrease in noise factor determined as the ratio of power spectrum maximum of electrical noise in a fine nerve strand to the corresponding value of the equivalent resistor in neurofilaments isolated from the sciatic nerve with blocked conduction in comparison with intact control. Noise factor can be used as a criterion for selection of intact fine nerve strands. Translated fromByulleten ‘Eksperimental’ noi Biologii i Meditsiny, Vol. 130, No. 8, pp. 151–154, August, 2000     

Implication of the hippocampus in the development of a pain syndrome in rats following sciatic nerve damage

Local destruction or electrostimulation of the hippocampus did not affect pain sensitivity thresholds in rats with intact sciatic nerve. In rats with transected sciatic nerve, local hippocampal damage accelerated the development of a pain syndrome considerably, while hippocampal electrostimulation delayed it so that 80% of the test rats did not appear to have been experiencing pain throughout the 45-day observation period. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 118, N ^o 8, pp. 120–122, August, 1994     

Regeneration of nerve fibers by laser irradiation of spinal nerve projections

The effect of short infrared laser irradiation on regeneration of nerve fibers in rat sciatic nerve was studied. Starting from the first day after nerve crushing, the projection of proximal portion of the nerve of the test group rats was transcutaneously stimulated by laser irradiation with the wavelength of 890 nm and total dose of 42 mJ/cm². The test rats demonstrated higher rate of restoration of cutaneous sensitivity in comparison with control rats, which were operated but not irradiated. The local vestibular reaction occurred 2 days earlier in the test group than in the control. On day 30 after crushing there were no significant differences in the number of myelinated fibers and mass of regenerating soleus muscle in the test and control groups. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 125, No. 3, pp. 348–350, March, 1998     

Insulin enhances l-dopa renal proximal tubule uptake: a regulatory mechanism impaired in insulin resistance

A stimulatory role for insulin in the uptake of neutral amino acids has been reported for a variety of tissues. Here we examine the effect of insulin on l-dopa uptake by proximal tubule cells (PT cells) isolated from control and fructose-fed rats (FR-rats, 10% w/v fructose solution in tap water), a model of insulin resistance. Insulin (200 U/ml) increased l-dopa uptake into PT cells by about 50% (705±186 vs.1117±140 pmol l-dopa/mg protein per minute) (p<0.05). The higher uptake correlated with a 40% increase in the number of high-affinity l-dopa transport sites (l-dopa 0.2 M) (0.59±0.05 vs. 0.82±0.09 pmol l-dopa/mg protein per minute), without changing their affinity. The effect of insulin was not modified by ouabain (1 mM), nocodazole (1–10 M) or colchicine (50–100 M), whereas it was abolished by cytochalasin D or latrunculin B (both 1 M). This suggests that the process is independent of Na⁺,K⁺-ATPase activity or the microtubule network but that it requires the integrity of the actin cytoskeleton. l-dopa transport by the low-affinity transport sites (l-dopa 5 M) was not affected by insulin, neither was the effect of insulin observed in PT cells isolated from FR-rats. In line with this, FR-rats showed lower renal l-dopa reabsorption as compared to control animals (81±4 vs. 51±9%). Taken together, our results support the involvement of insulin in the multifactorial regulation of renal l-dopa reabsorption.     

Protective effect of carnosine in hyperthermia

Under the conditions of hyperthermia, carnosine (β-alanine-l-histidine) normalizes tissue contents of lipid peroxidation products, cytochrome P-450, serotonin, and histamine in rats and increases their survival after extreme hyperthermia. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 124, No. 7, pp. 50–52, July, 1997     

Dexamethasone and vitamin B12 synergistically promote peripheral nerve regeneration in rats by upregulating the expression of brain-derived neurotrophic factor

Introduction

Dexamethasone and vitamin B₁₂ are currently used in the clinic to treat peripheral nerve damage but their mechanisms of action remain incompletely understood. In this study we hypothesized that dexamethasone and vitamin B₁₂ promote the production of endogenous neurotrophic factors, thereby enhancing peripheral nerve repair.

Material and methods

Ninety-six adult male Wistar rats were employed to establish a sciatic nerve injury model. They were then randomly divided into 4 groups to be subjected to different treatment: saline (group A), dexamethasone (group B), vitamin B₁₂ (group C), and dexamethasone combined with vitamin B₁₂ (group D). The walking behavior of rats was evaluated by footprint analysis, and the nerve regeneration was assessed by electrophysiological analysis and ultrastructural examination. The expression of brain-derived neurotrophic factor (BDNF), glial cell-derived neurotrophic factor, NT-3 and IL-6 in the injured sciatic nerves was detected by immunohistochemical and RT-PCR analysis.

Results

Dexamethasone and vitamin B₁₂ promoted the regeneration of myelinated nerve fibers and the proliferation of Schwann cells. Furthermore, dexamethasone and vitamin B₁₂ promoted the recovery of sciatic functional index and sensory nerve conduction velocity, and upregulated BDNF expression in the injured sciatic nerves.

Conclusions

Dexamethasone and vitamin B₁₂ promote peripheral nerve repair in a rat model of sciatic nerve injury through the upregulation of BDNF expression. These findings provide new insight into the neurotrophic effects of dexamethasone and vitamin B₁₂ and support the application of these agents in clinical treatment of peripheral nerve injury.     

Beneficial effects of treadmill training in experimental diabetic nerve regeneration

OBJECTIVES:

We investigated the effects of treadmill training (10 weeks) on hindlimb motor function and nerve morphometric parameters in diabetic rats submitted to sciatic nerve crush.

MATERIALS AND METHOD:

Wistar rats (n = 64) were divided into the following groups: non-diabetic; trained non-diabetic; non-diabetic with sciatic nerve crush; trained non-diabetic with sciatic nerve crush; diabetic; trained diabetic; diabetic with sciatic nerve crush or trained diabetic with sciatic nerve crush. Diabetes was induced by streptozotocin injection (50 mg/kg, iv). Hindlimb motor function was evaluated weekly by assessing sciatic functional indices, and the proximal and distal portions of the sciatic nerve were used for morphometric analysis.

RESULTS:

At 13 weeks post-injury, the distal nerve portion of all injured groups and the proximal nerve portion of the diabetic with sciatic nerve crush group presented altered morphometric parameters such as decreased myelinated fiber diameter (∼7.4±0.3µm vs ∼4.8±0.2µm), axonal diameter (∼5±0.2µm vs ∼3.5±0.1µm) and myelin sheath thickness (∼1.2±0.07µm vs ∼0.65±0.07µm) and an increase in the percentage of area occupied by endoneurium (∼28±3% vs ∼60±3%). In addition, in the non-diabetic with sciatic nerve crush group the proximal nerve portion showed a decreased myelinated fiber diameter (7.4±0.3µm vs 5.8±0.3µm) and myelin sheath thickness (1.29±0.08µm vs 0.92±0.08µm). The non-diabetic with sciatic nerve crush, trained non-diabetic with sciatic nerve crush, diabetic with sciatic nerve crush and trained diabetic with sciatic nerve crush groups showed normal sciatic functional index from the 4^th, 4^th, 9^th and 7^th week post-injury, respectively. Morphometric alterations in the proximal nerve portion of the diabetic with sciatic nerve crush and non-diabetic with sciatic nerve crush groups were either prevented or reverted to values similar to the non-diabetic group by treadmill training.

CONCLUSION:

Diabetic condition promoted delay in sciatic nerve regeneration. Treadmill training is able to accelerate hindlimb motor function recovery in diabetic injured rats and prevent or revert morphometric alterations in proximal nerve portions in non-diabetic and diabetic injured rats.     

Comparative analysis of brain electric activity after intraventricular administration of GABA and glutamate: It there any correlation between specific neurochemical modifications in the brain and EEG changes?

GABA,l-glutamate, and sodium hydroxybutyrate cause a decrease in the EEG power in the 7–12 Hz range. The latency of this decrease is 6–7 min after administration of GABA and 14–15 min after administration ofl-glutamate.d-Glutamate induces no changes in this range. It is suggested that modifications of EEG observed after administration ofl-glutamate reflect metabolic transformations of GABA. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 124, No. 8, pp. 174–177, August, 1997     

Effect of <Emphasis Type="SmallCaps">l</Emphasis>-carnitine supplementation and aerobic training on FABPc content and β-HAD activity in human skeletal muscle

Both regular physical exercise and carnitine supplementation exert a role in energy metabolism and may improve endurance capacity. We investigated whether a combination of long-term carnitine ingestion and exercise training reveals any interactive effects on cytosolic fatty acid-binding protein (FABPc) expression and β-hydroxyacyl CoA dehydrogenase (β-HAD) activity in human skeletal muscle. Twenty-eight untrained healthy males randomly divided into four experimental groups: a placebo (CON; n = 7), exercise training (ET; n = 7, 40 min session⁻¹, five times per week at 60% VO_2max), carnitine supplementation (CS; n = 7, 4 g day⁻¹), and exercise training and carnitine supplementation (CT; n = 7). Before and after 6-week treatment, muscle biopsy samples were taken from the vastus lateralis. Nonesterified carnitine and acid-soluble acylcarnitine concentrations were increased in CT (P < 0.05), and serum triacylglycerol concentration was elevated almost twofold in ET and CT (P < 0.05). No interactive effects in FABPc expression were shown from any of treatment groups. Although FABPc increased by 54% in ET compared to CON, it failed to reach statistical significance. In addition, there was no change in FABPc expression from any of experimental groups. Similar trends with FABPc contents were demonstrated in β-HAD activity. It is concluded that the combination of exercise training and l-carnitine supplementation does not augment in FABPc expression and β-HAD activity in human skeletal muscle indicating that combined treatment does not exert additive effect in fat metabolism. Thus l-carnitine supplementation would be unlikely to be associated with the enhanced exercise performance.     

Stimulation of 5-hydroxytryptamine nerve cells in dorsal and median raphe nuclei elevates blood glucose in rats

The role played by dorsal or median raphe nuclei in glucoregulation was investigated by stimulating these nuclei in normal rats and in rats with chemical ablation of the hydroxytryptamine (5-HT) nerve cells in these nuclei. Electrical stimulation of either dorsal or median raphe nuclei increased blood glucose or the in vivo voltammetric signal of hypothalamic 5-OH-indole in normal rats; the increase in blood glucose level or the hypothalamic 5-OH-indole release was proportional to the intensity of stimulation. Microinjection of kainic acid or l-glutamate at the same sites also produced hyperglycemia or stimulated the hypothalamic 5-OH-indole release. This stimulation-induced hyperglycemia was significantly reduced by pretreatment of animals with spinal transection or adrenalectomy. In addition, selective destruction of the hypothalamic 5-HT nerve fibers, produced by administration of 5,7-di-hydroxytryptamine (a 5-HT nerve depletor) into both dorsal and median raphe regions, reduced the magnitude of the hyperglycemic responses to electrical stimulation of either dorsal or median raphe nuclei. The data indicate that stimulation of ascending 5-HT pathways in the rat's brain increases the adrenal-sympathetic efferent activity and leads to hyperglycemia.     

Effects of fluorinated inositols on the phosphoinositide metabolism and the proliferation of Trypanosoma cruzi

Inositol has been cited as being essential for the growth of micro-organisms and animals. Its action rests mostly in the formation of a set of inositol-containing lipids, including phosphatidylinositol and its phosphorylated derivatives. To evaluate the functional responses coupled to the phosphoinositide metabolism in Trypanosoma cruzi we used myo-inositol and its six fluorinated analogues. Their uptake into epimastigotes was characterised using tritium-labeled myo-inositol and monodeoxyfluoro-myo-inositols. The analogues were tested for their ability to inhibit [³H]-myo-inositol incorporation into phosphoinositides and the proliferation of epimastigotes and amastigotes. The results showed differences between T. cruzi and mammalian systems in the responses to the fluorinated analogues. We found that the 3-, 5- and 6-fluoro analogues did not enter the cells but had an inhibitory effect on the incorporation of the radioactive inositol into lipids and on the amastigotes' and epimastigotes' replication. The most effective inhibitor, 1-D-6-deoxy-6-myo-inositol, had no effect on mammalian cell division. Received: 12 June 1998 / Accepted: 15 September 1998     

化学去细胞异体神经联合骨髓间充质干细胞修复损伤坐骨神经的生物力学评价

文题释义： 生物力学：是应用力学原理和方法对生物体中的力学问题定量研究的生物物理学分支,其研究范围从生物整体到系统、器官(包括血液、体液、脏器、骨骼等),从鸟飞、鱼游、鞭毛和纤毛运动到植物体液的输运等。生物力学的基础是能量守恒、动量定律、质量守恒定律并加上描写物性的本构方程。生物力学研究的重点是与生理学、医学有关的力学问题。依研究对象的不同可分为生物流体力学、生物固体力学和运动生物力学等。 周围神经研究热点和发展趋势：周围神经损伤的治疗已经取得了突破性的进展,但由于周围神经走行长、结构复杂、功能多样,损伤后其自身和靶器官会发生改变,而且是动态的、有时间效应的改变,因此以整体统一的理念研究周围神经损伤是今后研究重点。如何将基础研究与临床相结合,最终实现成果转化服务于患者,是研究者们的努力方向。国内外学者对自体神经损伤移植替代材料的研究从未间断过。随着组织工程和生物力学的发展,同种异体神经和人工神经已逐渐应用于临床,去细胞神经移植物也已取得了很好的临床效果。背景：以拉伸力学指标评估化学去细胞异体神经联合骨髓间充质干细胞治疗坐骨神经损伤的效果,目前鲜有报道。 目的：评估化学去细胞异体神经联合骨髓间充质干细胞移植治疗坐骨神经损伤的效果。 方法：将45只SD大鼠随机分为自体神经移植组、化学去细胞异体神经移植组、化学去细胞异体神经联合骨髓间充质干细胞移植组,每组15只,制备10 mm坐骨神经损伤模型,分别以自体神经、化学去细胞异体神经、化学去细胞异体神经联合骨髓间充质干细胞修复坐骨神经损伤,术后20周,进行坐骨神经电生理检测和坐骨神经单向拉伸实验。 结果与结论：①化学去细胞异体神经联合骨髓间充质干细胞移植组与自体神经移植组波幅值、运动传导速度值大于化学去细胞异体神经移植组(P < 0.05);②化学去细胞异体神经联合骨髓间充质干细胞移植组与自体神经移植组拉伸弹性限度应变、弹性限度应力、最大应变、最大应力大于化学去细胞异体神经移植组(P < 0.05);③结果表明,化学去细胞异体神经联合骨髓间充质干细胞移植对坐骨神经损伤具有明显的修复效果。ORCID: 0000-0002-1029-8117(吴志峰) 中国组织工程研究杂志出版内容重点：干细胞;骨髓干细胞;造血干细胞;脂肪干细胞;肿瘤干细胞;胚胎干细胞;脐带脐血干细胞;干细胞诱导;干细胞分化;组织工程     

Structural abnormalities do not explain the early functional abnormalities in the peripheral nerves of the streptozotocin diabetic rat

The streptozotocin (STZ)-diabetic rat, the most commonly employed model of experimental diabetic neuropathy, is characterised by a reduction in nerve conduction velocity, pain threshold and blood flow. Whether or not structural abnormalities underlie these functional abnormalities is unclear. 10 adult male Sprague–Dawley STZ-diabetic rats (diabetes duration 27 d) and 10 age-matched (23 wk) control animals were studied. Motor nerve conduction velocity (m s⁻¹) was significantly reduced in diabetic (41.31±0.8) compared with control (46.15±1.5) animals ( P <0.001). The concentration of sciatic nerve glucose ( P <0.001), fructose ( P <0.001) and sorbitol ( P <0.001) was elevated, and myoinositol ( P <0.001) was reduced in diabetic compared with control animals. Detailed morphometric studies demonstrated no significant difference in fascicular area, myelinated fibre density, fibre and axon areas as well as unmyelinated fibre density and diameter. Endoneurial capillary density, basement membrane area and endothelial cell profile number did not differ between diabetic and control animals. However, luminal area ( P <0.03) was increased and endothelial cell area ( P <0.08) was decreased in the diabetic rats. We conclude there is no detectable structural basis for the reduction in nerve conduction velocity, pain threshold or blood flow, observed in the streptozotocin diabetic rat.     

Oral administration ofl-arginine, a nitric oxide precursor, decreases nociceptive sensitivity in rats

Tail-flick test was used to evaluate the effect of orally administeredl-arginine on nociceptive sensitivity of albino rats, which produced a) analgesia at 30 min postadministration lasting about 1.5 h (100 mg/kg); b) short-term analgesia (50 mg/kg); and c) no analgesic effect (250 mg/kg).d-Arginine (100 mg/kg) did not affect the nociceptive sensitivity. A significant NO increase took place in cerebral cortex at 30 min postadministration ofl-arginine in the given doses. At 1 h postadministration ofl-arginine in doses of 50 and 250 mg/kg, cortical NO content was lower than that in control animals. Analgesic effect ofl-arginine is presumably related to additional synthesis of NO. This effect seems to be not directly produced by NO, but is realized via other transmitter systems. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 124, No. 11, pp. 498–501, November, 1997     

The Na+-dependent binding of [3H]l-aspartate in thaw-mounted sections of rat forebrain

Binding of [³H]l-aspartate to thaw-mounted coronal sections of frozen rat forebrain was strong in grey regions of telencephalon (neocortex, hippocampus and neostriatum), but it was weaker and unevenly distributed in diencephalon. At low nanomolar concentrations of ligand used in the present studies, [³H]l-aspartate binding was strongly inhibited by l-threo-3-hydroxyaspartate and l-trans-pyrrolidine-2,4-dicarboxylate, compounds known to be substrate/inhibitors of the high affinity uptake of l-glutamate and l-aspartate. None of the typical ligands for the glutamate and aspartate receptors, 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX), N-methyl-d-aspartate and kainate, produced a strong enough inhibition (only CNQX at 100 M weakly inhibited) of the Na⁺-dependent [³H]l-aspartate binding to suggest that [³H]l-aspartate was bound to the receptor binding sites. Furthermore, the binding was absolutely dependent on the presence of Na⁺ in the incubation medium. It is concluded that [³H]l-aspartate is a ligand suitable for autoradiographic studies of the distribution of Na⁺-dependent, high affinity uptake of acidic amino acids in the central nervous system (CNS). However, feasibility of using [³H]l-aspartate as a specific marker of glutamatergic and/or aspartergic synapses in the CNS requires further investigation.