Effect of skin temperature on the ion reabsorption capacity of sweat glands during exercise in humans

The effect of skin temperature on the ion reabsorption capacity of sweat glands during exercise in humans is unknown. In this study, eight healthy subjects performed a 60-min cycling exercise at a constant intensity (60% VO_2max) under moderate (25°C) and cool (15°C) ambient temperatures at a constant relative humidity of 40%. The sweating rate (SR), index of sweat ion concentration (ISIC) by using sweat conductivity, esophageal temperature (Tes), mean skin temperature, and heart rate (HR) were measured continuously under both ambient temperatures. The SR and ISIC were significantly lower at the cool ambient temperature versus the moderate temperature. There were no significant differences in the changes in HR and esophageal temperature between these ambient temperature conditions, while the mean skin temperature was significantly lower at the cool ambient temperature by almost 3°C (P<0.05). The slopes of the relationships between Tes and the SR and ISIC were significantly lower and the thresholds of these relationships were significantly higher at the cool ambient temperature (P<0.05). The ion reabsorption capacity of the sweat glands was significantly lower (P<0.05) in a cool environment (0.21±0.04 vs. 0.52±0.06 mg/cm²/min at 15 and 25°C, respectively) as evaluated using the relationships for SR and ISIC. The results suggest that the ion reabsorption capacity of the sweat glands is influenced by skin temperature during exercise in humans.     

Atrial natriuretic factor (ANF) does not affect ion transport in human intestine but does in porcine intestine

The aim of this study was to test whether atrial natriuretic factor (ANF) exerts any effect on human intestinal ion transport, and the porcine intestine was used as a positive control of ANF's effects. Tissues from human proximal (n = 6) and distal (n = 6) colons, and from distal ileum (n = 6) were mounted in Ussing chambers, and short circuit current (I_sc) was measured subsequent to serosal application of ANF (10^--⁶ m), 8–Br-cyclic guanosine monophosphate (8–Br-cGMP) (10^--⁴ m), and theophylline (10^--² m). ANF did not affect I_sc whereas 8–Br-cGMP increased I_sc by 28 (8–53), 16 (3–36), and 16 (5–41) μA cm^-2 in the distal colon (DC), proximal colon (PC) and distal ileum (DI), respectively. Likewise, transepithelial potential difference (PD) became more negative by 5.0 (0.6–8.9), 2.5 (0.4–4.0) and 0.9 (0.3–2.3) mV in DC, PC, and DI, respectively, subsequent to addition of 8–Br-cGMP. I_sc and PD were further increased by theophylline. Additional radio-isotope flux studies in human colon revealed that ANF did not affect electroneutral sodium and chloride transport either. For comparison, ANF (10^--⁶ m) was administered to large intestinal tissues from young pigs in which ANF induced a significant increase in I_sc which was comparable to the 8–Br-cGMP response in humans. The porcine I_sc response was partly inhibited by chloride-free solution on the serosal side, by serosal application of bumetanide (10^--⁴ m) and BaCl₂ (10^--³ m), and mucosal application of the chloride-channel blocker diphenylamine-2–carboxylate (DPC) (10^--³ m). Mucosal amiloride (10^--⁵ m) pre-treatment reduced baseline I_sc but did not affect the porcine intestinal I_sc response to ANF. In vitro radio-autography demonstrated specific binding sites for ANF in porcine distal colon, whereas no apparent labelling was observed in human distal colon. These findings suggest that the lack of effect of ANF on sodium and chloride transport in human distal ileum and colon is probably due to lack of ANF receptors. In the porcine intestine, however, the I_S0 response induced by ANF seems to involve stimulation of electrogenic chloride secretion, whereas electrogenic sodium absorption seems unaffected.     

Heavy-ion-induced mutations in the gpt delta transgenic mouse: comparison of mutation spectra induced by heavy-ion,X-ray,and gamma-ray radiation

Heavy-ion radiation accounts for the major component of absorbed cosmic radiation and is thus regarded as a significant risk during long-term manned space missions. To evaluate the genetic damage induced by heavy particle radiation, gpt delta transgenic mice were exposed to carbon particle irradiation and the induced mutations were compared with those induced by reference radiations, i.e., X-rays and gamma-rays. In the transgenic mouse model, deletions and point mutations were individually identified as Spi(-) and gpt mutations, respectively. Two days after 10 Gy of whole-body irradiation, the mutant frequencies (MFs) of Spi(-) and gpt were determined. Carbon particle irradiation significantly increased Spi(-) MF in the liver, spleen, and kidney but not in the testis, suggesting an organ-specific induction of mutations by heavy-ion irradiation. In the liver, the potency of inducing Spi(-) mutation was highest for carbon particles (3.3-fold increase) followed by X-rays (2.1-fold increase) and gamma-rays (1.3-fold increase), while the potency of inducing gpt mutations was highest for gamma-rays (3.3-fold increase) followed by X-rays (2.1-fold increase) and carbon particles (1.6-fold increase). DNA sequence analysis revealed that carbon particles induced deletions that were mainly more than 1,000 base pairs in size, whereas gamma-rays induced deletions of less than 100 base pairs and base substitutions. X-rays induced various-sized deletions and base substitutions. These results suggest that heavy-ion beam irradiation is effective at inducing deletions via DNA double-strand breaks but less effective than X-ray and gamma-ray irradiation at producing oxidative DNA damage by free radicals.     

A composite poly-hydroxybutyrate-glial growth factor conduit for long nerve gap repairs

There is considerable evidence that peripheral nerves have the potential to regenerate in an appropriate microenvironment. We have developed a novel artificial nerve guide composed of poly 3-hydroxybutyrate (PHB) filled with glial growth factor (GGF) suspended in alginate hydrogel. Gaps of 2-4 cm in rabbit common peroneal nerve were bridged using a PHB conduit containing either GGF in alginate hydrogel (GGF) or alginate alone (Alginate), or with an empty PHB conduit (Empty). Tissues were harvested 21, 42 and 63 days post-operatively. Schwann cell and axonal regeneration were assessed using quantitative immunohistochemistry. At 21 days, addition of GGF increased significantly the distance of axonal and Schwann cells regeneration in comparison with that observed in Alginate and Empty conduits for both gap lengths. The axons bridged the 2-cm GGF conduits gap by 63 days, with a comparable rate of regeneration seen in 4-cm conduits. Schwann cells and axonal regeneration quantity was similar for both gap lengths in each group. However, at all time points the quantity of axonal and Schwann cells regeneration in GGF grafts was significantly greater than in both Alginate and Empty conduits, the latter showing better regeneration than Alginate conduits. The results indicate an inhibitory effect of alginate on regeneration, which is partially reversed by the addition of GGF to the conduits. In conclusion, GGF stimulates a progressive and sustainable regeneration increase in long nerve gap conduits.     

Influence of macrolides on mucoid alginate biosynthetic enzyme from Pseudomonas aeruginosa

Objective: The long-term administration of erythromycin (EM), clarithromycin (CAM) or azithromycin (AZM) has generally resulted in a favorable outcome for patients with diffuse panbronchiolitis (DPB) infected with mucoid Pseudomonas aeruginosa. To elucidate the mechanism involved, the influence of macrolides on mucoid alginate production by P. aeruginosa was investigated in vitro.
Methods: The macrolides used in this study were EM with a 14-membered ring, AZM with a 15-membered ring, midecamycin (MDM) with a 16-membered ring, and CP-4305, which has had mycarose removed from MDM, The effects of macrolides on mucoid P. aeruginosa were investigated by quantitative assay of alginate production and inhibition of guanosine diphospho-D-mannose dehydrogenase activity.
Results: After incubation with EM, AZM and CP-4305, the structural material of P. aeruginosa biofilm was distorted, and the enzymatic activity of GDP-D-mannose dehydrogenase, the most important enzyme in mucoid alginate biosynthesis, was inhibited. However, these effects were not observed with the 16-membered macrolide MDM.
Conclusions: The basic mechanism of clinical efficacy seen characteristically in 14- or 15-membered macrolides for patients with airway biofilm disease depends on the ability of such macrolides to inhibit alginate production by P. aeruginosa. Furthermore, this suggests that the inhibitory effect observed with 14-, 15- and 16-membered macrolides may depend on the sugar chain connected with the macrolide ring.     

Muscle relaxant action of excitatory amino acid antagonists

Antagonists of neuronal excitation induced by dicarboxylic amino acids were tested in genetically spastic rats of the Han-Wistar strain. These animals exhibit an increased muscle tone which can be measured as a spontaneous tonic activity in the electromyogram of the gastrocnemius-soleus muscle. Compounds that block excitation due to N-methyl-D-aspartic acid reduced the spontaneous activity measured in the electromyogram in a dose-related manner. The most potent compounds, 2-amino-7-phosphonoheptanoic and kynurenic acids were effective muscle relaxants when given either intraperitoneally or intracerebroventricularly. 2-Amino-5-phosphonopentanoic acid possessed much weaker muscle relaxant activity, while L-glutamic acid diethylester was inactive by either route. The results suggest that blockade of N-methyl-D-aspartic acid receptors results in a myorelaxant effect. Specific antagonists of excitation at N-methyl-D-aspartic acid receptors may provide a new class of muscle relaxants.     

钾离子对体外培养中枢神经髓鞘形成的影响──一种新的体外培养中枢神经脱髓鞘模型的建立

本文应用组织培养和电镜等方法研究了ＫＣＩ对体外培养中枢神经系统髓鞘形成的影响。结果表明：体外培养Ｂ６Ｃ３小鼠小脑组织髓鞘形成的关键期是１０～１４ｄ，在１０～１２ｄ时体外培养的小脑组织对ＫＣＩ最为敏感；当培养液内ＫＣＩ浓度达到３０ｍｍｏｌ／Ｌ时，即可完全抑制髓鞘形成。本文对钾离子引起体外培养中枢神经组织脱髓鞘的机制进行了讨论。     

Kv11.1 channel subunit composition includes MinK and varies developmentally in mouse cardiac muscle

The Kv11.1 (also ERG1) K(+) channel underlies cardiac I(Kr), a current that contributes to repolarization in mammalian heart. In mice, I(Kr) current density decreases with development and studies suggest that changes in the structure and/or properties of the heteromultimeric I(Kr)/Kv11.1 channel are responsible. Here, using immunohistochemistry, we report that total Kv11.1 alpha subunit protein is more abundant in neonatal heart and is distributed throughout both adult and neonatal ventricles with greater abundance in epicardia. Immunoblots reveal that the alpha subunit alternative splice variant, Kv11.1a, is more abundant in adult heart while the Kv11.1b variant is more abundant in neonatal heart. Additionally, MinK channel subunit protein is shown to co-assemble with Kv11.1 protein and is more abundant in neonatal heart. In summary, Kv11.1/I(Kr) channel composition varies developmentally and the higher I(Kr) current density in neonatal heart is likely attributable to higher abundance of Kv11.1/I(Kr) channels, more specifically, the Kv11.1b splice variant.     

免疫磁性海藻酸钠载药纳米微球的制备与评价

靶向治疗系统是目前研究的热点,用微乳化-离子交联方法制备包覆阿霉素的碳包铁/海藻酸钠复合纳米微球,以水溶性碳二亚胺为交联剂,将载药微球与单抗Hab18连接,制备出了免疫磁性药物纳米微球.对该免疫磁性微球的理化性能进行了表征,同时检测了免疫磁性微球中抗体的活性和免疫磁性微球与靶细胞的体外结合情况,结果表明,免疫磁性药物纳米微球平均粒径约为171.2nm,外观为球型,铁含量为14.6%,载药量为10.8%,且具有强磁响应性和长时间药物缓释效果.同时在体外该微球能够与靶细胞特异性结合.这种免疫磁性药物纳米微球有望成为一种优良的靶向肿瘤药物载体.     

胶原“人工皮”的研制及其生物物理特性

胶原“人工皮”由聚乙烯膜、尼龙筛网和胶原组成。动物实验证明,胶原“人工皮”应用于创面,可减少死腔,增加与创面的粘附力,控制细菌侵入和防止液体丢失。该“人工皮”可以替代猪皮或尸体皮应用于外科手术