Stretch of mammalian nerve in vitro: effect on compound action potentials

Stretch of nerve has been reported to decrease the amplitude of the compound action potential (CAP) with a complete block appearing in approximately 30 minutes. But for the most part, those experiments were carried out in vivo, and it is generally accepted that the failure of responses was due to a closure of vessels supplying the nerve with a resulting ischemia and anoxia. These studies were undertaken to determine if stretch of nerve has effects that are independent of interference with its vascular supply. In the studies, lengths of rat sciatic and dog peroneal nerves were removed and placed in a chamber supplied with oxygen in which their CAPs were continuously elicited and recorded. This in vitro preparation obviated interference with the nerve's metabolism on stretching. We have previously shown that the form change termed 'beading,' appearing within 10 seconds and reversing as quickly on relaxation, can be elicited with tensions of only several grams. We wished to determine if stretch adequate to produce beading could alter CAPs with the same rapidity. Tensions below 2 g had little effect. On applying tensions of 10-100 g, levels well above those needed to bead the fibers, both increases and decreases of CAP amplitude were seen. The changes occurred within 10 seconds of stretch application, the time at which beading arises with stretch. Although the decreases of CAP amplitudes could be accounted for by beading, the degree of CAP change did not correspond to the amount of tension applied. We hypothesize that the constrictions in the beaded fibers increase axial resistivity and diminish local currents so as to block conduction. The lack of an increasing degree of decreased CAP amplitude with increases in tension is ascribed to the inhibition of elongation offered by the collagen fibrils present in nerve. Collagenase applied to nerves allowed a further increase in length, producing a 'hyperbeading,' showing much longer lengths of beading constrictions on stretch. This would further increase axial resistance and is taken to account for the greater decreases of CAP amplitudes seen following collagenase treatment. To account for those cases where increases of CAP amplitude were seen on stretch, we hypothesize that stretch can also cause an increase in the excitability of the nodes. The outcome of stretch in any given nerve would be the resultant of two opposing actions; beading of the internodes causes a decrease of local currents leading to block of CAPs, while an increased excitability of the nodes acts to augment the responses.     

潍坊市城区双向转诊制度实施情况及政策建议

目前,在社区卫生服务双向转诊制度实施中还面临很多障碍,要使双向转诊制度落到实处,真正发挥它应有的作用,仍然存在许多不尽人意的地方。文章通过从政府及其有关部门角度、患者角度、医疗保险机构角度、媒体角度等多方面,提出了促进双向转诊的主要措施。     

False Tendon‐Related Polymorphic Ventricular Tachycardia

A 39‐year‐old woman showed nonsustained polymorphic ventricular tachycardia (PVT) during light physical activity. Cardiac multidetector row computed tomography demonstrated false tendons, one of which proved to be the focus triggering premature ventricular contraction (PVC) in electrophysiological studies. The triggered PVC arose during the diastolic period, which might have caused tension in the false tendon. Radiofrequency catheter ablation targeting the triggered PVC by pace mapping was performed and proved partially effective against PVT. (PACE 2012;35:e341–e344)     

In-vivo stretch of term human fetal membranes

IntroductionFetal membranes (FM) usually fail prior to delivery during term labor, but occasionally fail at preterm gestation, precipitating preterm birth. To understand the FM biomechanical properties underlying these events, study of the baseline in-vivo stretch experienced by the FM is required. This study's objective was to utilize high resolution MRI imaging to determine in-vivo FM stretch.MethodsEight pregnant women (38.4 ± 0.4wks) underwent abdominal-pelvic MRI prior to (2.88 ± 0.83d) caesarean delivery. Software was utilized to determine the total FM in-vivo surface area (SA) and that of its components: placental disc and reflected FM. At delivery, the SA of the disc and FM in the relaxed state were measured. In-vivo (stretched) to delivered SA ratios were calculated. FM fragments were then biaxially stretched to determine the force required to re-stretch the FM back to in-vivo SA.ResultsTotal FM SA, in-vivo vs delivered, was 2135.51 ± 108.47 cm² vs 842.59 ± 35.86 cm²; reflected FM was 1778.42 ± 107.39 cm² vs 545.41 ± 22.90 cm², and disc was 357.10 ± 28.08 cm² vs 297.18 ± 22.14 cm². The ratio (in-vivo to in-vitro SA) of reflected FM was 3.26 ± 0.11 and disc was 1.22 ± 0.10. Reflected FM re-stretched to in-vivo SA generated a tension of 72.26 N/m, corresponding to approximate pressure of 15.4 mmHg. FM rupture occurred at 295.08 ± 31.73 N/m corresponding to approximate pressure of 34 mmHg. Physiological SA was 70% of that at rupture.DiscussionFM are significantly distended in-vivo. FM collagen fibers were rapidly recruited once loaded and functioned near the failure state during in-vitro testing, suggesting that, in-vivo, minimal additional (beyond physiological) stretch may facilitate rapid, catastrophic failure.     

Influence of a New Monofilament Polyester Mesh on Inflammation and Matrix Remodeling

ABSTRACT

Synthetic mesh is widely used for hernia repairs, but mesh-induced chronic inflammatory responses may lead to postoperative complications. We previously showed an elevated response to multifilament polyester (PE) versus monofilament polypropylene (PP) and polytetrafluoroethylene (PTFE) meshes, but it is unclear whether this discrepancy is due to the differences in chemical composition or filament structure. This study compares the influence of a newly available monofilament PE mesh to that of multifilament PE, monofilament PP, and monofilament PTFE on the expression of genes important in inflammation and extracellular matrix remodeling in a rat model. Full thickness abdominal wall defects were corrected with onlay repair or suture repair with no mesh. Explants were harvested 7 or 90 days after repair and divided for histology and mRNA analyses using real-time quantitative polymerase chain reaction arrays to profile expression at the tissue-mesh interface. Monofilament PE elicited a reduced foreign body reaction compared to multifilament PE, corresponding with reduced mRNA expression of important inflammatory cytokines and matrix metalloproteinases (MMPs). Unexpectedly, monofilament PE also resulted in markedly reduced mRNA expression of tumor necrosis factor and MMPs 3 and 9 compared to the widely-used monofilament PP mesh. Findings from this study revealed that both chemical composition and filament structure are important mesh characteristics that may affect a patient's wound healing response and clinical outcome, and should be considered by the surgeon when choosing a particular mesh. Although clinical studies are warranted, results in a rodent model suggest that monofilament PE may be more beneficial than the multifilament form for certain hernia repairs.     

Early Necrectomy in Deep Burns of Aesthetically and Functionally Important Areas

Deep burns of aesthetically and functionally important body areas in children may in their later growth and development have a decisive role. Of the total number (2743) of hospitalized children at the Burns Department of the Pediatric Surgery in Zagreb in the last ten years. deep burns of some aesthetically and functionally important body areas were separated and the results of the application of the early necrectomy and immediate grafting method, as recommended by Jan?ekovi?, are analysed. It is concluded that the results, due to the strict and minute application of the method (considered are individual technically important details and solutions) are good in aesthetic and even more so in the functional sense. Very fast recovery of the functions as well as the fact that up till now no surgical corrections for functional disorders were necessary in analyzed areas, along with already known advantages of the early surgical treatment, undoubtfully speak for its application.     

Digital analysis yields more reliable and accurate measures of dermal and epidermal thickness in histologically processed specimens compared to traditional methods

Changes in the thickness of the dermis and epidermis have been described in the scenario of tissue expansion as well as inflammatory skin processes (psoriasis, contact hypersensitivity and so on). These changes have previously been quantified using ocular micrometers to obtain and then average a limited number of spot measurements, leading to suboptimal accuracy. We describe a rapid method of using freely available ImageJ software to analyze digitized images of fixed skin specimens. By determining the cross‐sectional area and surface length of a skin layer, a simple calculation produces more accurate and reproducible measurements of its thickness compared to historical methods, with excellent inter‐rater reliability.     

硫酸软骨素酶ABC和环磷酸腺苷缓释组织工程 支架的构建

目的:制备一种可生物降解有效安全的硫酸软骨素酶ABC(ChABC)和环磷酸腺苷(cAMP)缓释组织工程支架,使药物缓慢稳定释放,降低局部应用时对神经的刺激,促进中枢神经系统损伤后神经的修复和轴突的再生。方法:应用电纺丝技术制作的含ChABC及cAMP的聚碳酸亚丙酯及壳聚糖缓释组织工程支架,分析支架直径、载药量、包封率等参数,然后以磷酸盐缓冲液为体外释药介质观察组织工程支架的药物释放速度、药物的失活率及支架的降解速度。结果:ChABC和cAMP缓释组织工程支架在聚碳酸亚内酯质量浓度为8%、电压为10～15 kV、距离为15～20 cm时可以纺出纤维直径约3μm的平滑支架,单纯聚碳酸盐内酯纤维光滑,直径均一,壳聚糖微球光滑,聚碳酸亚内酯与壳聚糖混合后电纺丝形成的支架呈串珠样结构,其能缓慢持续释放有活性ChABC和cAMP,12 d后支架降解失重率约7%。结论:应用电纺丝方法成功制备含ChABC及cAMP的聚碳酸盐内酯及壳聚糖组织工程支架,其药物稳定释放,局部应用无神经刺激,可生物降解。     

Safety assessment for octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)-propionate (CAS Reg. No. 2082-79-3) from use in food contact applications

Octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (CAS Reg. No. 2082-79-3), currently marketed as Irganox 1076 (I-76), is a sterically hindered phenolic antioxidant used in a variety of organic substrates, including those used in the manufacture of food contact articles. In 2012, the US Food and Drug Administration (USFDA), Office of Food Additive Safety (OFAS), initiated a post-market re-evaluation of the food contact applications of I-76. This project aimed to ensure that current dietary exposures from the use of I-76 in food contact articles are accurately captured and the safety assessment considered all relevant and available toxicological information. To accomplish these aims, the USFDA reviewed the available toxicological studies and chemistry information on food contact applications of I-76. Based on this in-depth analysis, a NOAEL of 64 mg/kg-bw/d (female rats) from a chronic rat study and a cumulative estimated dietary intake (CEDI) of 4.5 mg/p/d, was used to calculate a margin of exposure (MOE) of ∼850. We concluded that the previous and current exposure levels provide an adequate margin of safety (MOS) and remain protective of human health for the regulated uses.