Application of problem-based self-designed experiments in physiology laboratory teaching.

A physiology laboratory course plays an important role in improving the scientific abilities of medical students. This study involved a teaching reform based on problem-based self-designed experiments in a physiology laboratory course. The study subjects were divided into two groups, i.e., students enrolled in 2019 were assigned to the traditional course control group (n = 146) and students enrolled in 2021 were assigned to the improved course test group (n = 128). Students in the test group were required to conduct self-designed experiments based on the questions for each experimental theme, in addition to completing the specified experimental items. At the end of the course, the differences in academic achievements between the two groups were compared. The results showed that compared to the control group, the students in the test group spent less time finishing the specified experimental items (P < 0.05). More students in the test group obtained good results in the operation assessment for the specified experiments (P < 0.05), and a significant increase in the number of winners in discipline-wise competitions, participants in scientific research projects, and academic publications was observed in the test group. Most of the students in the test group agreed that the self-designed experiment promoted their scientific thinking, helped them better understand theoretical knowledge, and improved their hands-on operation and team cooperation abilities. Our research showed that our teaching reform promoted students' self-directed learning and problem-solving abilities, stimulated their enthusiasm for scientific research, and was conducive to the cultivation of innovative medical talents.NEW & NOTEWORTHY This study involved a teaching reform based on problem-based self-designed experiments in a physiology laboratory course. Students in the test group were required to conduct self-designed experiments based on questions for each experimental theme, in addition to completing the specified experimental items. The results showed that the teaching reform promoted the students' self-directed learning and problem-solving ability, stimulated their enthusiasm for scientific research, and was conducive to cultivating innovative medical talents.

The neuroprotective effect of apigenin against OGD/R injury in rat hippocampal neurons.

To investigate the effects of apigenin on the injury caused by oxygen and glucose deprivation in neurons and the underlying mechanisms, primary cultured rat hippocampal neurons were incubated with apigenin for 90 min before a 2-h oxygen and glucose deprivation followed by a 24-h reperfusion (OGD/R). Subsequently, cell viability, lactate dehydrogenase (LDH) leakage rate, apoptotic rate of neurons and activity of the sodium pump were assessed. In addition, activity of the sodium pump was also examined in the hippocampus of SD rats injected intraperitoneally with apigenin 90 min before a 10-min global cerebral ischemia/24-h reperfusion. The results showed that cell viability and activity of the sodium pump markedly decreased but LDH leakage rate and apoptotic rate significantly increased in OGD/R-treated neurons. However, pretreatment with apigenin (20-50µmol/L) reversed the changes dose-dependently. Compared to sham controls, activity of the sodium pump was significantly suppressed in global ischemia/reperfusion rats; application of apigenin (200mg/kg) restored the activity of the sodium pump. Furthermore, the neuroprotective effect of apigenin was blocked partly by the sodium pump inhibitor ouabain. Our findings provide the evidence that apigenin has a neuroprotective effect against OGD/R injury and the protective effect may be associated with its ability to improve sodium pump activity.

[Progress on matrix metalloproteinase in axonal regeneration].

Matrix metalloproteinases (MMPs) are zinc-dependent endopeptidases. MMPs can degrade and remodel extracellular matrix, also active or inactive many molecules attaching to matrix including receptors, growth factors and cytokines, so that injury-induced MMPs can change the extracellular environment to affect the axonal regeneration in central nervous system. In this review, with spinal cord injury (SCI) as an example we discuss the effects of MMPs on inflammation, neuronal viability, extracellular molecules, glial scar and axonal remyelination, which are all important to axonal regeneration.

[LIM kinases and their roles in the nervous system].

LIM kinase-1 (LIMK1) and LIM kinase-2 (LIMK2) are kinases that have serine/threonine and tyrosine dual specificity. Although they show significant structural similarity, LIMK1 and LIMK2 have different expression patterns, subcellular localization, and functions. Activation of LIM kinases regulates the downstream of Rho GTPases, and influences the architecture of the actin cytoskeleton by regulating the activity of cofilin. Recent studies have shown that LIM kinases play important roles in the nervous system. For example, development of the central nervous system is reliant upon the presence of LIMK1, and deletion of Limk1 gene is involved in the development of the human genetic disorder Williams syndrome. Therefore, it is of vital physiological significance to investigate the neuronal function of LIM kinases. In this review, we outline the structure, phosphorylation regulation and neuronal function of LIM kinases, so as to provide new ideas for the treatment of these neurological diseases.

New insights into the biological roles of immune cells in neural stem cells in post-traumatic injury of the central nervous system.

Traumatic injuries in the central nervous system, such as traumatic brain injury and spinal cord injury, are associated with tissue inflammation and the infiltration of immune cells, which simultaneously affect the self-renewal and differentiation of neural stem cells. However, the tissue repair process instigated by endogenous neural stem cells is incapable of restoring central nervous system injuries without external intervention. Recently, resident/peripheral immune cells have been demonstrated to exert significant effects on neural stem cells. Thus, the restoration of traumatic injuries in the central nervous system by the immune intervention in neural stem cells represents a potential therapeutic method. In this review, we discuss the roles and possible mechanisms of immune cells on the self-renewal and differentiation of neural stem cells along with the prognosis of central nervous system injuries based on immune intervention. Finally, we discuss remaining research challenges that need to be considered in the future. Further elucidation of these challenges will facilitate the successful application of neural stem cells in central nervous system injuries.

[P21-activated kinases and their role in the nervous system].

P21-activated kinases (PAK) participate in a variety of important cellular activities, such as cytoskeleton remodeling, cell migration, cell cycle regulation, and apoptosis or survival. PAK also has an important impact on brain development, neuronal differentiation, and regulation of synaptic plasticity in the nervous system. PAK abnormalities result in diseases including cancer, Parkinson's disease (PD), Alzheimer's disease (AD) and neural retardation. Therefore, it is of vital physiological significance to investigate the neuronal function of PAK. In this paper we review the advancement of research on the neuronal biological function and the underlying mechanisms of PAK.

[Comparison of mannitol and hypertonic saline in treatment of intracranial hypertension of rabbits].

OBJECTIVE: To compare the effects of mannitol and hypertonic saline (HS) in treatment of intracranial hypertension (ICH) of rabbits. METHODS: The animal mode of ICH was established by perfusing artificial cerebrospinal fluids (aCSF) with controlled pressure into the cerebral ventricles of rabbits. The mean arterial pressure, respiratory rate, tidal volume, perfusion rate of aCSF and water content of cerebrum were investigated in rabbits with ICH after a single bolus of 20% mannitol (5 ml/kg), 7.5% HS (2.2 ml/kg) or 23.4% HS (2.2 ml/kg). RESULTS: After the intracranial pressure was elevated from 15 cmH2O to 75 cmH2O, the mean arterial pressure was increased and the tidal volume was decreased. After treatment by 20% mannitol, 7.5% HS or 23.4% HS, the increased percentage of mean arterial pressure and the decreased percentage of tidal volume were similar to the changes in control group. However, the perfusion rate of CSF was increased and water content of cerebrum was decreased after treatment by either 20% mannitol or 23.4% HS, but not by 7.5% HS. No different effects were found between 20% mannitol and 23.4% HS. CONCLUSION: With the similar osmotic burden, 20% mannitol is more effective in treating ICH than 7.5% HS. With higher osmotic load, the efficacy of HS is enhanced, and 23.4% HS may be used as an alternative to mannitol in treatment of ICH.

[Marrow mesenchymal stem cell transplantation with sodium alginate gel for repair of spinal cord injury in mice].

OBJECTIVE: To investigate the effects of sodium alginate gels on marrow mesenchymal stem cell transplantation for repair of spinal cord injury (SCI) in mice. METHODS: In the present study, effects of different sterilization methods and concentrations of sodium alginate gels were examined. Marrow mesenchymal stem cells (mMSCs) were isolated from mice and cultured. Cells were cultured with sodium alginate gels and MTT assay was applied to determine the cell viability. Mice spinal cord injury was induced by spinal cord transection. mMSCs were transplanted into the cavity of injured spinal cord with sodium alginate gels. The effects of sodium alginate gel were assessed by BMS scales and immunofluorescence staining for NF-200. RESULTS: Compared with liquid form, solid form sodium alginate gel prepared with high pressure vapor sterilization had a better effect on cell viability. SCI mice treated with 10 % sodium alginate gel and mMSCs achieved higher score in BMS scale as well as higher expression of NF-200 compared with the untreated SCI group. CONCLUSION: Sodium alginate gel prepared with solid form sterilization induces mMSCs proliferation and thus can be used as the carrier of stem cell in treatment of SCI.

Nischarin-siRNA delivered by polyethylenimine-alginate nanoparticles accelerates motor function recovery after spinal cord injury.

A previous study by our group found that inhibition of nischarin promotes neurite outgrowth and neuronal regeneration in Neuro-2a cells and primary cortical neurons. In recent years, more and more studies have shown that nanomaterials have good prospects in treatment of spinal cord injury. We proposed that small interfering RNA targeting nischarin (Nis-siRNA) delivered by polyethyleneimine-alginate (PEI-ALG) nanoparticles promoted motor function recovery in rats with spinal cord injury. Direct microinjection of 5 µL PEI-ALG/Nis-siRNA into the spinal cord lesion area of spinal cord injury rats was performed. From day 7 after surgery, Basso, Beattie and Bresnahan score was significantly higher in rats from the PEI-ALG/Nis-siRNA group compared with the spinal cord injury group and PEI-ALG/Control-siRNA group. On day 21 after injection, hematoxylin-eosin staining showed that the necrotic area was reduced in the PEI-ALG/Nis-siRNA group. Immunohistochemistry and western blot assay results confirmed successful inhibition of nischarin expression and increased protein expression of growth-associated protein-43 in the PEI-ALG/Nis-siRNA group. These findings suggest that a complex of PEI-ALG nanoparticles and Nis-siRNA effectively suppresses nischarin expression, induces expression of growth-associated protein-43, and accelerates motor function recovery after spinal cord injury.

Bamboo leaf extract improves spatial learning ability in a rat model with senile dementia.

Senile dementia (SD) is a syndrome characterized by progressive neurological deterioration. Treatment for the disease is still under investigation. Bamboo leaf extract (B-extract) has been known for its biological efficacy in anti-oxidant and anti-cancer activities. However, study on B-extract for its protection against dementia is very limited. The effect of B-extract on a rat model with SD was examined. B-extract improved spatial learning ability of the dementia rats. The hippocampus of dementia model rats showed reduced levels of acetylcholine (ACh), epinephrine (E), norepinephrine (NE), and dopamine (DA), and increased activities of acetylcholine esterase (AChE) and monoamine oxidase (MAO). Treatment with B-extract 20 mg/(kg·d) for 7 weeks significantly inhibited the enzyme activity compared with untreated dementia rats, and raised the levels of ACh, E, and DA in the hippocampus. In addition, treatment with B-extract elevated the level of γ-aminobutyric acid (GABA), but reduced the level of glutamate (Glu) in the brain. These data suggest that B-extract might be a potential drug in treating impairment of spatial memory in dementia rats by regulating the central neurotransmitter function.

[Negative inotropic effect of meperidine in rat ventricular muscle and the underlying mechanism].

The purpose of the present study was to investigate the effect of meperidine on rat ventricular muscle. Cardiac function was assessed in Langendorff-perfused rat hearts and intracellular calcium level was recorded in enzymatically isolated rat ventricular myocytes using spectrofluorometric techniques. To explore the underlying mechanism, whole-cell configuration of patch-clamp technique was used to record L-type Ca(2+) current. The results showed that meperidine decreased the product of heart rate and left ventricular developed pressure (LVDP HR), maximal rate of the left ventricular pressure increase (LV +dP/dt(max)) and decrease (LV -dP/dt(max)), but increased left ventricular end-diastolic pressure in a dose-dependent manner (0-1000 micromol/L). Meperidine also produced a dose-dependent reduction in electrically induced [Ca(2+)](i) transient amplitude and an increase in diastolic [Ca(2+)](i) baseline level, but did not alter the caffeine (20 mmol/L) induced Ca(2+) release from intracellular ryanodine-sensitive Ca(2+) stores. Meperidine at 100 micromol/L inhibited L-type Ca(2+) current to 67.4 10.1% of control but did not affect the voltage dependency of activation and inactivation. The inhibitory effect of meperidine on Ca(2+) current could not be prevented by pretreatment with the opioid receptor antagonist naloxone. These data suggest that meperidine exerts a negative inotropic effect by inhibiting L-type Ca(2+) current. The lack of effect of naloxone implies that the action is independent of the opioid receptor.

[NO/cGMP signal pathway involved in the disturbance of calcium homeostasis in vascular smooth muscle during the late phase of sepsis].

OBJECTIVE: To evaluate the alterations in calcium metabolism of the vascular smooth muscle of rat thoracic aorta in the late phase of sepsis and to investigate the involvement of nitric oxide (NO)/cyclic-GMP(cGMP) signal transduction pathway in the sepsis-induced vascular hyporeactivity. METHODS: Male Sprague-Dawley rats were subjected to sepsis by cecal ligation and puncture (CLP). Eighteen hours post CLP, rat aortic rings were removed for measurement of contractile responses to vasoconstrictors by using organ bath technique. RESULT: In endothelium intact aortic rings from CLP rats, concentration-contraction curves to phenylephrine (PE) and high KCl were significantly decreased when compared with those from control rats. The transient contraction induced by PE in calcium-free Krebs solution and the concentration-dependent contraction to CaCl(2)in KCl-depolarized medium were also markedly reduced. The hyporeactivity to vasoconstrictors was completely reversed by pretreatment either with aminoguanidine (AMG), a selective inducible nitric oxide synthase inhibitor, or with 1H [1,2,4] oxadiazolo[4,3-a] quininoxalin-1-one(ODQ), an inhibitor of NO-sensitive guanylyl cyclase. CONCLUSION: A generalized impairment in calcium handling in vascular smooth muscle,including the calcium influx through the voltage-operated and receptor-operated channels and calcium release from intracellular calcium stores, is involved in vascular hyporeactivity during the late phase of sepsis. The NO/cGMP signal transduction pathway might be involved in this defect in vascular smooth muscle.

[Effects of pethidine on cardiac electrophysiological properties].

OBJECTIVE: To investigate the effects of pethidine on electrophysiological properties of the isolated ventricular myocytes and the underlying mechanism. METHODS: Langendorff was applied to perfuse rat heart model and whole-cell current clamp and voltage clamp techniques were used. RESULTS: Pethidine decreased heart rate (HR) in a concentration dependent manner and caused severe atrioventricular block (AVB) at >or=250 micromol/L. Pethidine reduced action potential amplitude and maximal rate of depolarization, prolonged action potential duration. Pethidine at 100 micromol/L decreased sodium currents (I(Na)), transient outward potassium currents (I(to)), delayed rectifier potassium currents (I(k)) and L-type calcium currents (I(Ca.L)) to (60.7+/-6.9)%, (55.4+/-5.6)%, (65.1+/-8.0)% and (67.4+/-10.1)% of control levels,respectively. These effects could be recovered by washout. Naloxone, an opioid receptor antagonist, could not abolish the effects of pethidine on ionic currents. CONCLUSION: Pethidine decreased HR and induced AVB, which may be related to the inhibition of I(Na), I(to), I(k) and I(Ca-L) of heart. The depression of cardiac currents is not mediated by opioid receptor.

Construction of a eukaryotic expression vector pEGFP-C1-BMP-2 and its effect on cell migration.

OBJECTIVE: Bone morphogenetic proteins (BMPs) are known to play an important role in bone and cartilage development. Recent research has shown that BMPs may induce tumorigenesis and promote tumor to spread, but the molecular mechanisms have not been elucidated. The aim of the present study was to investigate the regulatory function of BMP-2 in the migration of COS-7 cells and the underlying mechanisms. METHODS: Human BMP-2 genetic fragment was amplified and introduced into the pEGFP-C1 vector. After being confirmed by XhoI and BamHI digestion analyses and DNA sequencing, the recombinant pEGFP-C1-BMP-2 plasmid was transfected into COS-7 cells. The influence of BMP-2 on cell migration and cofilin activity was detected by cell scratch assay and Western blotting. RESULTS: The recombinant pEGFP-C1-BMP-2 was effectively expressed in COS-7 cells. An increased phosphorylation of both LIMK1 and cofilin and an enhancement of cell migration were observed in cells with overexpression of BMP-2. CONCLUSIONS: A recombinant pEGFP-C1-BMP-2 vector was successfully constructed and overexpression of BMP-2 regulated the activities of the downstream molecules of the Rho GTPase signaling pathway, which might contribute to the enhancement of cell migration.