Inhibition of Na+ channel currents in rat myoblasts by 4-aminopyridine

Our previous study revealed that 4-aminopyridine (4-AP), a specific blocker of A-type current, could also inhibit inward Na+ currents (I(Na)) with a state-independent mechanism in rat cerebellar granule cells. In the present study, we report an inhibitory effect of 4-AP on voltage-gated and tetrodotoxin (TTX)-sensitive I(Na) recorded from cultured rat myoblasts. 4-AP inhibited I(Na) amplitude in a dose-dependent manner between the concentrations of 0.5 and 10 mM without significant alteration in the activation or inactivation kinetics of the channel. By comparison to the 4-AP-induced inhibitory effect on cerebellum neurons, the inhibitory effect on myoblasts was enhanced through repetitive pulse and inflected by changing frequency. Specifically, the lower the frequency of pulse, the higher the inhibition observed, suggesting that block manner is inversely use-dependent. Moreover, experiments adding 4-AP to the intracellular solution indicate that the inhibitory effects are localized inside the cell. Additionally, 4-AP significantly modifies the properties of steady-state activation and inactivation kinetics of the channel. Our data suggest that the K+ channel blocker 4-AP inhibits both neuron and myoblast Na+ channels via different mechanisms. These findings may also provide information regarding 4-AP-induced pharmacological and toxicological effects in clinical use and experimental research.     

Apoptotic markers on lymphocytes and monocytes are unchanged during single hemodialysis sessions using either regenerated cellulose or polysulfone membranes

BACKGROUND: There is an increased rate of apoptosis of peripheral blood mononuclear cells (PBMCs) in patients undergoing hemodialysis (HD), but little is known about how different dialysis membranes may contribute to the process. We, therefore, studied the influence of two different dialysis membranes on apoptotic markers during HD. METHODS: 8 healthy controls and 8 patients on regular HD 3 times per week were enrolled in this cross-controlled study. Patients received HD using polysulfone and then regenerated cellulose dialysis membranes for one week each, sequentially. Serum was collected for C-reactive protein (CRP) detection; flow cytometry with dual antibody staining was used to measure the apoptotic markers Fas (CD95), FasL (CD 178) and TNF-R2 (CD120b) in T cells (CD3+), B cells (CD19+), and monocytes (CD14+) at 0, 15, 120 and 240 min after starting HD. We also measured total leukocyte numbers and differential white cell counts. RESULTS: Hemodialysis patients revealed lymphocytopenia, monocytopenia, higher CRP levels and higher Fas and TNF-R2 expression on lymphocytes and monocytes at baseline when compared with normal controls. Leukocyte numbers, including neutrophils, lymphocytes and monocytes, dropped significantly after 15 min of dialysis. There were no significant differences in Fas levels during hemodialysis on T and B lymphocytes or on monocytes. T lymphocyte FasL (CD 178) levels remained unchanged throughout the process. There was a significantly lower overall level of CD120b at 15 min of HD, whereas this marker was higher on monocytes after dialysis. There were no significant differences in the levels of apoptotic markers between the two membranes. CONCLUSION: Our results suggest that uremia itself contributes to PBMC apoptosis. The two different dialysis membranes used in this study did not influence apoptotic markers on PBMCs significantly, but increased TNF-R2 expression on monocytes during a single dialysis session.     

The ethics of using genetic engineering for sex selection

It is quite likely that parents will soon be able to use genetic engineering to select the sex of their child by directly manipulating the sex of an embryo. Some might think that this method would be a more ethical method of sex selection than present technologies such as preimplantation genetic diagnosis (PGD) because, unlike PGD, it does not need to create and destroy "wrong gendered" embryos. This paper argues that those who object to present technologies on the grounds that the embryo is a person are unlikely to be persuaded by this proposal, though for different reasons.     

骨质疏松研究和诊断若干问题之管见

近年来,我国的骨质疏松和其他代谢性骨病的研究发展迅速,很多单位在这方面做了大量工作,取得了很大进步,但与国际先进水平和现实要求相比,还存在一定差距和问题。充分认识这些差距,着力解决现存的主要问题,是我们的重要任务之一。     

脂肪来源成体干细胞分化为内皮细胞的潜能

目的研究脂肪来源的干细胞是否具有向内皮细胞分化的潜能.方法从成人脂肪组织分离脂肪来源的成体干细胞,检测其生长特性、表型以及成骨、脂肪和神经的能力.在血管内皮细胞生长因子(VEGF)、碱性成纤维细胞生长因子(bFGF)诱导下,免疫组织化学和逆转录-聚合酶链反应检测内皮细胞标志及脂肪来源的成体干细胞输入下肢缺血小鼠体内后能否分化成血管内皮细胞.结果脂肪来源成体干细胞在体外能迅速扩增,表达血管内皮细胞生长因子受体2(VEGFR-2,Flk1),具有分化成骨、成脂肪和成神经的能力;在VEGF、bFGF诱导下,能分化成有功能的内皮细胞,改善缺血状况.结论脂肪来源成体干细胞不仅具有间充质细胞的分化潜能,还具有内皮干/祖细胞性质,可以用于血管新生的细胞治疗.     

Nursing care in the conduct of alveolar lavage

Pulmonary alveolar proteinosis (PAP) is a rare disease reported to affect adults between the ages of 20 and 50, in a male:female ratio of 2-3:1. Alveolar lavage is the most effective proven treatment. This article introduces PAP, alveolar lavage and nursing intervention in preparation, during, and after the procedure, and home care. We hope this article can provide new information on the nursing care necessary for patients with PAP.     

Relation between activities of the cortex and vibrissae muscles during high-voltage rhythmic spike discharges in rats

Paroxysmal 5- to 12-Hz high-voltage rhythmic spike (HVRS) activities, which are accompanied by whisker twitching (WT), are found in Long Evans rats, but the function of these HVRS activities is still debated. In four major functional hypotheses of HVRS discharges, i.e., alpha tremor, attention/mu rhythm, idling/mu rhythm, and absence seizure, the first two hypotheses emphasize WT behavior in HVRS bouts. Whisker movement is primarily determined by activation of intrinsic and extrinsic muscles. To clarify the role of WT in HVRS activities, simultaneous recording of the activities from the cortex and intrinsic/extrinsic and neck muscles were performed. Most HVRS bouts (68.8%) revealed no time-locked WT behavior in a 2-h recording session. In addition, WT primarily arose from active protraction due to activation of intrinsic muscles followed by passive retraction. A small portion of WT resulted from activation of both vibrissae muscles with dynamic frequency-dependent phase shifts. Onset of the rhythmic vibrissae EMG significantly lagged behind HVRS onset, and the mean duration of vibrissae muscle activity was one-third to a one-half of a HVRS bout. Moreover, a greater number of HVRS bouts were associated with a longer HVRS duration and higher oscillation frequency. Oscillation frequencies of HVRS activities without WT behavior were significantly lower than those with WT. Under peripheral sensory/motor blockade by xylocaine injection, oscillation frequencies of HVRS bouts significantly decreased, but no remarkable changes in the number or duration of HVRS bouts were observed. Compared with vibrissa muscle activity during WT and exploratory whisking, the duration of muscular activity in each cycle was apparently longer during whisking bouts. Based on these results, overemphasis of the role of WT on HVRS activities might not be appropriate. Instead, HVRS discharges may be associated with absence seizure or idling state. In addition, peripheral inputs, including WT, may elevate the oscillation frequency of HVRS bouts. Moreover, different muscular controls may exist between WT and whisking.