Study on the temperature characteristics of fast capacitance in patch clamp experiments / 生物医学工程学杂志

Patch clamp is a technique that can measure weak current in the level of picoampere (pA). It has been widely used for cellular electrophysiological recording in fundamental medical researches, such as membrane potential and ion channel currents recording, etc. In order to obtain accurate measurement results, both the resistance and capacitance of the pipette are required to be compensated. Capacitance compensations are composed of slow and fast capacitance compensation. The slow compensation is determined by the lipid bilayer of cell membrane, and its magnitude usually ranges from a few picofarads (pF) to a few microfarads (μF), depending on the cell size. The fast capacitance is formed by the distributed capacitance of the glass pipette, wires and solution, mostly ranging in a few picofarads. After the pipette sucks the cells in the solution, the positions of the glass pipette and wire have been determined, and only taking once compensation for slow and fast capacitance will meet the recording requirements. However, when the study needs to deal with the temperature characteristics, it is still necessary to make a recognition on the temperature characteristic of the capacitance. We found that the time constant of fast capacitance discharge changed with increasing temperature of bath solution when we studied the photothermal effect on cell membrane by patch clamp. Based on this phenomenon, we proposed an equivalent circuit to calculate the temperature-dependent parameters. Experimental results showed that the fast capacitance increased in a positive rate of 0.04 pF/℃, while the pipette resistance decreased. The fine data analysis demonstrated that the temperature rises of bath solution determined the kinetics of the fast capacitance mainly by changing the inner solution resistance of the glass pipette. This result will provide a good reference for the fine temperature characteristic study related to cellular electrophysiology based on patch clamp technique.

Monitoring osseointegrated prosthesis loosening and fracture using electrical capacitance tomography

A noncontact, noninvasive, electrical permittivity imaging technique is proposed for monitoring loosening of osseointegrated prostheses and bone fracture. The proposed method utilizes electrical capacitance tomography (ECT), which employs a set of noncontact electrodes, arranged in a circular fashion around the imaging area, for electrical excitations and measurements. An inverse reconstruction algorithm was developed and implemented to reconstruct the electrical permittivity distribution of the interrogated region from boundary capacitance measurements. In this study, osseointegrated prosthesis phantoms were prepared using plastic rods and Sawbone femur specimens, which were subjected to prosthesis loosening and fracture monitoring tests. The results demonstrated that the spatial location and extent of prosthesis loosening and bone fracture could be estimated from the ECT reconstructed permittivity maps. The resolution of the reconstructed images was further enhanced by a limited region tomography algorithm, and its accuracy in terms of identifying the severity, location, and shape of bone fracture was also investigated and compared with conventional full region tomography.

Effect of fast capacitance compensation method on improving the action potential firing accuracy of nerve cell / 生物医学工程学杂志

Patch-clamp is used to study all sorts of ionic channels and their regulations with measuring pA current of cell ionic channel, but the fast capacitance (C-fast) compensation and slow capacitance (C-slow) compensation transient currents are caused by measuring objects and measuring instruments themselves which will change the properties of action potentials. The present paper firstly discusses the C-Fast transient currents affecting membrane capacitance and membrane potential, and then draws a conclusion that the changes of membrane potential affect the properties of action potential through analyzing the changes of membrane potential in H-H model. Based on this conclusion, we discuss the influence mechanisms mainly through the analysis of traditional C-fast compensation errors, and focus discussion on the shape of electrode capacitance affecting C-fast. This method can not only improve the compensation speed greatly, but also improve the compensation precision from the electrode shape as much as possible.

Bulk-like endocytosis plays an important role in the recycling of insulin granules in pancreatic beta cells

Although bulk endocytosis has been found in a number of neuronal and endocrine cells, the molecular mechanism and physiological function of bulk endocytosis remain elusive. In pancreatic beta cells, we have observed bulk-like endocytosis evoked both by flash photolysis and trains of depolarization. Bulk-like endocytosis is a clathrin-independent process that is facilitated by enhanced extracellular Ca(2+) entry and suppressed by the inhibition of dynamin function. Moreover, defects in bulk-like endocytosis are accompanied by hyperinsulinemia in primary beta cells dissociated from diabetic KKAy mice, which suggests that bulk-like endocytosis plays an important role in maintaining the exo-endocytosis balance and beta cell secretory capability.

Test for dangerous limits of capacitor energy / 中国医疗器械杂志

For dangerous limits of capacitor energy, according to national standards of medical device regulations' test requirement, we analysis it and list its test methods and requirement. According to capacitor energy's formation and characteristics, we put forward a simple method for its test and calculation.

Low bone density management via capacitively coupled electrical fields and low intensity pulsed ultrasound in hemiparetic cerebral palsy

Osteoporosis is being increasingly recognized in pediatric practice as a consequence of several factors. These include the increasing complexity of chronic conditions and the associated treatments managed by pediatricians. In addition, the improved care provided to children with chronic illness has led to many of them living long enough to develop osteoporosis. Many children with cerebral palsy have diminished bone mineral density and the application of capacitively coupled electrical fields and low intensity pulsed ultrasound aim to improve the formation of bone cells and so may be helpful in the management of such cases. In this study, capacitively coupled electrical fields and low intensity pulsed ultrasound was conducted to investigate its effect on bone mineral density in spastic diaplegic cerebral palsy. Twenty spastic hemiparetic children were the sample of this work. There were divided randomly into two equal groups. Bone mineral densities were measured before and after six months of the application of the treatment program. Group A [control] received the physiotherapy program, while group B [study] received capacitively coupled electrical fields and low intensity pulsed ultrasound in addition to the same treatment program given to group A. Significant improvement were observed in all measuring variables when comparing the post-treatment results in both groups in favor of group B. Capacitively coupled electrical fields and low intensity pulsed ultrasound therapy may be considered as one of the most helpful methods of physiotherapy in management of low bone density in spastic hemiparetic cerebral palsied children

Residual voltage of terms and test method / 中国医疗器械杂志

This paper describes 5 national standards related to the term on the residual voltage with different indicators. Compare the advantages and disadvantages of various test methods. Finally, give suggestions on improving the testing method.

Modeling and experimental study on frequency-domain electricity properties of biological materials / 生物医学工程学杂志

Frequency-domain electricity properties of four objects, including bullfrog skin, bullfrog muscle, triply distilled water and 0.9% NaCl, were tested in the range of 100Hz-10MHz using home-made electrode and measuring system. The experimental results showed that the resistance of 0.9% NaCl decreased dramatically, that the amplitude frequency characteristics of bullfrog's muscle and skin were similar, but that of triply distilled water did not change significantly. The frequency dependence of 0.9% NaCl showed that the electrode had great influence on the measuring system, so a new equivalent circuit model based on the electrode system was needed. These findings suggest that the new five-parameter equivalent circuit model, which embodies considerations on the interaction between electrodes and tissues, is a reasonable equivalent circuit for studying the electrical characteristics of biological materials.

Electrical properties of moist limestone samples in the frequency range 1Hz-10[7] from Abu Rawash area

The dielectric constant and electrical resistivity of Abu Rawash limestone samples are measured at some varying atmospheric relative humidity and room temperature [almost equal to] 22C [degree sign]] in the frequency range [1 Hz- 10[7] Hz]. Little increase in the atmospheric humidity varies resistivities by 4 orders or more of magnitude. Variations in the dielectric constant of the same order can also be obtained. Frequency dependent impedance measurements indicate that, the overall electrical response of a rock sample is controlled by one or more of three conduction mechanisms, which can be identified as: [i] conduction through adsorbing water layer on solid surfaces, [ii] conduction through mass transportation or diffusion through pore spaces filled with water and [iii] high frequency [radio frequency and higher] conduction. Cation exchange capacity [CEC] plays the essential role in defining the electrical properties of solid-solution interfaces. Mass transport or diffusion impedance, as affected by measuring electrode properties, may also be called diffusion controlled impedance. It takes place at frequencies lower than the chemical reaction. The high frequency conduction mechanism is controlled by the intrinsic properties of the sample constituents

Comparison of Transepidermal Water Loss, Capacitance and pH Values in the Skin between Intrinsic and Extrinsic Atopic Dermatitis Patients

Atopic dermatitis (AD), with the prevalence rate of around 10 to 15%, is characterized by an intensely pruritic skin lesions with typical distribution and morphology. Recently, AD is divided into extrinsic type (ADe) and intrinsic type (ADi) according to the laboratory findings and associated diseases. ADe is well-known for high IgE level, positive response to food- or aero-allergens, whereas ADi has clinically similar skin lesions and distribution patterns of AD with normal serum IgE levels, negative in vitro test for environmental or food allergens and without associated atopic diseases. To instrumentally evaluate the differences of skin involvement and functions between ADi and ADe, we checked the transepidermal water loss (TEWL), capacitance and pH in both types of childhood AD and age-matched control. The proportion of ADi was around 20% in all AD patients (10/51). Our experiment suggested possible differences between ADi and ADe. Antecubital fossa is a famous involvement site of childhood type of AD, where both types of AD patients showed higher TEWL and decreased capacitance. ADe patients showed increased TEWL in all sites and lower hydration in 4 sites, whereas ADi patients showed no significant differences of TEWL and hydration in forehead, cheek, and back of leg.