Increase in conduction velocity in myelinated nerves due to stretch – An experimental verification

BackgroundBased on published experimental evidence, a recent publication revealed an anomalous phenomenon in nerve conduction: for myelinated nerves the nerve conduction velocity (NCV) increases with stretch, which should have been the opposite according to existing concepts and theories since the diameter decreases on stretching. To resolve the anomaly, a new conduction mechanism for myelinated nerves was proposed based on physiological changes in the nodal region, introducing a new electrical resistance at the node. The earlier experimental measurements of NCV were performed on the ulnar nerve at different angles of flexion, focusing at the elbow region, but left some uncertainty for not reporting the lengths of nerve segments involved so that the magnitudes of stretch could not be estimated.AimsThe aim of the present study was to relate NCV of myelinated nerves with different magnitudes of stretch through careful measurements.MethodEssentially, we duplicated the earlier published NCV measurements on ulnar nerves at different angles of flexion but recording appropriate distances between nerve stimulation points on the skin carefully and assuming that the lengths of the underlying nerve segment undergoes the same percentages of changes as that on the skin outside.ResultsWe found that the percentage of nerve stretch across the elbow is directly proportional to the angle of flexion and that the percentage increase in NCV is directly proportional to the percentage increase in nerve stretch. Page’s L Trend test also supported the above trends of changes through obtained p values.DiscussionOur experimental findings on myelinated nerves agree with those of some recent publications which measured changes in CV of single fibres, both myelinated and unmyelinated, on stretch. Analyzing all the observed results, we may infer that the new conduction mechanism based on the nodal resistance and proposed by the recent publication mentioned above is the most plausible one to explain the increase in CV with nerve stretch. Furthermore, interpreting the experimental results in the light of the new mechanism, we may suggest that the ulnar nerve at the forearm is always under a mild stretch, with slightly increased NCV of the myelinated nerves

Возможности флуоресцентной визуализации в оценке реваскуляризации гетеротопически трансплантированного сегмента трахеи приматов

Objective: to assess the potentials of using indocyanine green fluorescence angiography in evaluating revascularization of tissue-engineered construct that was obtained from the decellularized biological matrix of primate trachea, including using mesenchymal stem cells, after heterotopic tracheal allotransplantation. Material and methods. Tracheas were obtained from two male hamadryas baboons. After decellularization, 4 cm segments of tracheas were implanted under the lateral part of the latissimus dorsi in two healthy primates, one after recellularization with mesenchymal stem cells (animal 1), and the second without recellularization (animal 2). Immunosuppressive therapy was not performed. Blood flow in the transplanted segment of the trachea was evaluated 60 days after transplantation by surgical isolation of the flap of the latissimus dorsi with the transplanted segment of the trachea, while maintaining blood flow through the thoracodorsal artery. Indocyanine green near-infrared fluorescence angiography was visualized using a FLUM-808 multispectral fluorescence organoscope. Results. Sixty days after implantation, the tracheal cartilaginous framework macroscopically appeared to be intact in both animals, tightly integrated into the muscle tissue. The framework retained its natural color. After intravenous injection of indocyanine green, the tracheal vessels were visualized in both animals. Intercartilaginous vessels and portions of the cartilaginous semi-rings devoid of vessels were clearly distinguished. The entire implanted segment was almost uniformly vascularized. No local disruptions in blood supply were observed. The fluorescence brightness of the tracheal vessels was 193 ± 17 cu and 198 ± 10 cu in animals 1 and 2, respectively. The average muscle brightness in the implantation zone was 159 ± 9 cu and 116 ± 8 cu in animals 1 and 2, respectively. Conclusion. Indocyanine green fluorescence angiography is characterized by high-contrast images and high sensitivity. This facilitates vascular patency visualization and allows to assess the degree of neoangiogenesis after experimental transplantation of the tracheal segment, at different stages of experiment, without euthanizing the animal.Цель. Определение возможности использования индоцианиновой флуоресцентной ангиографии для оценки реваскуляризации тканеинженерной конструкции, полученной на основе децеллюляризированного биологического матрикса трахеи приматов, в том числе с использованием мезенхимных стволовых клеток, после ее гетеротопической аллотрансплантации. Материал и методы. Донорами трахеи послужили два самца павиана гамадрила. После децеллюляризации участки донорских трахей, по 4 см каждый, имплантированы под боковой участок широчайшей мышцы спины двум здоровым приматам, одному после рецеллюляризации мезенхимными стволовыми клетками (животное 1), второму – без проведения рецеллюляризации (животное 2). Иммуносупрессивную терапию не проводили. Наличие кровотока в трансплантированном сегменте трахеи оценивали через 60 суток после трансплантации путем хирургического выделения лоскута широчайшей мышцы спины с трансплантированным сегментом трахеи с сохранением кровотока по торакодорзальной артерии. Визуализацию инфракрасной индоцианиновой флуоресцентной ангиографии проводили с помощью мультиспектрального флуоресцентного органоскопа «FLUM-808». Результаты. Через 60 суток после имплантации хрящевой каркас трахеи макроскопически представлялся сохранным у обоих животных, плотно интегрированным в мышечную ткань, естественного цвета. После внутривенного введения индоцианина зеленого у обоих животных удалось визуализировать сосуды трахеи, четко различались межхрящевые сосуды и участки хрящевых полуколец, лишенные сосудов, весь имплантированный сегмент практически равномерно васкуляризирован, локальных нарушений кровоснабжения не отмечалось. Яркость флуоресценции сосудов трахеи у животного 1 составила 193 ± 17 у. е., у животного 2 – 198 ± 10 у. е., в то время как средняя яркость мышцы в зоне имплантации у животного 1 – 159 ± 9 у. е., а у животного 2 – 116 ± 8 у. е. Заключение. Индоцианиновая флуоресцентная ангиография характеризуется высокой контрастностью получаемых изображений, высокой чувствительностью, что может позволить визуализировать проходимость сосудистой сети и оценить степень неоангиогенеза после экспериментальной трансплантации сегмента трахеи на разных этапах эксперимента без эвтаназии животного

A simultaneous mobile e-learning environment and application

The purpose of the present study was to design a mobile learning environment that enables the use of a teleconference application used in simultaneous e-learning with mobile devices and to evaluate this mobile learning environment based on students' views. With the mobile learning environment developed in the study, the students are able to follow a teleconference application realized by using appropriate mobile devices. The study was carried out with 8 post-graduate students enrolled in Karadeniz Technical University (KTU), Department of Computer Education and Instructional Technologies (CEIT), Graduate School of Natural and Applied Science. The students utilized this teleconference application using mobile devices supporting internet access and Adobe Flash technology. Of the 8 students, 4 accessed the system using EDGE technology and 4 used wireless internet technology. At the end of the application, the audio and display were delayed by 4-5 seconds with EDGE technology, and were delayed by 7-8 seconds with wireless internet technology. Based on the students' views, it was concluded that the environment had some deficiencies in terms of quality, especially in terms of the screen resolution. Despite this, the students reported that this environment could provide more flexibility in terms of space and time when compared to other simultaneous distance education applications. Although the environment enables interaction, in particular, the problem of resolution caused by screen size is a disadvantage for the system. When this mobile learning application is compared to conventional education environments, it was found that mobile learning does have a role in helping the students overcome the problems of participating in learning activities caused by time and space constraints