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An electrical field was induced in a recalcitrant nonunion of the tibia by a symmetrical, sinusoidal signal of 5 volts peak-to-peak amplitude and 60 KHz frequency applied through surface electrodes with the power supply strapped to the thigh. After 6 months of treatment in a short leg cast, the nonunion healed.
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Experiments on skin moisture, i.e. the hydration state of the outer epidermis, were undertaken using three different types of equipment, i.e. the Skicon-100 and Corneometer CM 420 hydrometers and the Servo Med EPI evaporimeter. The studies included 10 healthy volunteers. Water was applied to test sites on the forearm and the palm of the hand, and effects monitored by the three methods. Parallel increases in conductance, capacitance and transepidermal water loss were registered for a duration of about 5 min. The Skicon-100 was more sensitive for measurement of increased hydration, while the Corneometer CM 420 might be more sensitive for measurement of decreased hydration. Inter- and intra-individual variations were minor with all instruments. According to reproducibility studies, the Corneometer CM 420 was more accurate than the Skicon-100. Technical experiments indicated that the Corneometer CM 420 depicts changes of hydration down to a depth of 0.1 mm, while the Skicon-100 measures very superficially. In conclusion, both hydrometers were deemed relevant and valid for assessment of skin moisture. The methods are complementary, and their combined use is recommended.
Readings made with condenser-ionization chamber systems are frequently suspect because significant changes in calibration can occur without being evident in the normal use of the instruments. These changes can be traced to physical causes that alter the voltage sensitivity of electrical capacitance. Thus, measurement of these electrical parameters will indicate whether or not a change in calibration has occurred. Formulas are presented of calculating such changes and determining which parameter is responsible. Good agreement was obtained between the results of calculations with these formulas and the results of radiation measurements made with a Victoreen Condenser R-Meter after several components had been deliberately maladjusted.
Based on the electromechanical equivalent circuit, the sandwich piezoelectric transducer with adjustable resonance frequency is studied. The underlying theory of frequency adjustment is its piezoelectric effect. In this paper, the influence of electric load impedance (including electric resistance, electric inductance, and electric capacitance) on the resonance frequency, the antiresonance frequency, and the effective electromechanical coupling coefficient is analyzed theoretically and experimentally. It is demonstrated that the electric load impedance can change the resonance frequency, the antiresonance frequency, and the effective electromechanical coupling coefficient. When the electric load resistance is increased, the resonance frequency and the antiresonance frequency are increased; the effective electromechanical coupling coefficient has a maximum value when the electric load resistance changes. When the electric load resistance becomes large, the effect of the electric load resistance on the effective electromechanical coupling coefficient is negligible. When the electric load inductance is increased, the resonance frequency and the antiresonance frequency are decreased, whereas the effective electromechanical coupling coefficient is increased. When the electric load capacitance is increased, the resonance frequency, the antiresonance frequency, and the effective electromechanical coupling coefficient are all decreased. It should be noted that when the electric load impedance becomes large, the effect of the electric load impedance on the resonance frequency, the antiresonance frequency, and the effective electromechanical coupling coefficient of a sandwich piezoelectric transducer becomes negligible.
The detailed mechanism behind the processes of DNA-dependent RNA transcription initiation is largely unknown. When transcription initiation factors bind DNA, a significant change in the electrostatic state of the complex can result. Using electrical capacitance measurements of solutions of the YY1 zinc finger transcription initiation factor and the adeno-associated viral P5 promoter DNA, we observed a specific dielectric change when a protein-DNA complex was formed. We propose that complexation results in electrostatic changes that may trigger the markedly different electrical behavior, and offer a possible explanation for our results.
The electrical capacitance of lipid membranes may increase by up to 50% on exposure to ionizing radiation. This is the consequence of lipid peroxidation induced by primary or secondary radicals of water radiolysis in the presence of oxygen. The polar products of this process give rise to an increase of the dielectric constant of the membrane. This in turn leads to the increase of membrane capacitance observed. An important consequence of this phenomenon is the reduction of the inner energy barrier between the two membrane/water interfaces influencing the movement of charged particles across the membrane. Thus the comparatively small change of the dielectric constant gives rise to the large increase in membrane conductance (by up to several orders of magnitude) observed in the presence of macrocyclic ion carriers of the valinomycin type (Strässle et al. 1987b). The results were obtained applying a novel method to measure time-dependent changes of the capacitance of planar lipid membranes.
This paper presents a new electronic methodology to detect DNA hybridization for rapid identification of diseases, as well as food and environmental monitoring on a genetic base. The proposed solution exploits a new (electrical) capacitive measurement circuit, not requiring any prior labeling of the DNA (as it is often the case with the commonly employed optical detection). The sensitivity, the reliability, and the reproducibility of this device have been evaluated by experiments performed with a (non-integrated) prototype implementation, easily integrable in IC and/or micro-fabricated lab-on-a-chip.
Very thin (2.3-5.5 nm) self-assembled organic dielectric multilayers have been integrated into organic thin-film transistor structures to achieve sub-1-V operating characteristics. These new dielectrics are fabricated by means of layer-by-layer solution phase deposition of molecular silicon precursors, resulting in smooth, nanostructurally well defined, strongly adherent, thermally stable, virtually pinhole-free, organosiloxane thin films having exceptionally large electrical capacitances (up to approximately 2,500 nF.cm(-2)), excellent insulating properties (leakage current densities as low as 10(-9) A.cm(-2)), and single-layer dielectric constant (k)of approximately 16. These 3D self-assembled multilayers enable organic thin-film transistor function at very low source-drain, gate, and threshold voltages (<1 V) and are compatible with a broad variety of vapor- or solution-deposited p- and n-channel organic semiconductors.
In the extremely preterm infant, high transepidermal water loss (TEWL) can result in severe dehydration. TEWL has been attributed to the structural properties of the epidermis but might also be influenced by mechanisms that facilitate water transport. To investigate whether aquaporins (AQP) may be involved in the extreme losses of water through immature skin, we examined the presence and cellular distributions of AQP-1 and AQP-3 in embryonic and adult rat skin by immunohistochemistry. The expression of AQP mRNA in skin was analyzed with the use of semiquantitative reverse transcription-PCR. In rat pups of different embryonic (E) and postnatal (P) ages (days), TEWL and skin hydration were measured. AQP-1 was detected in dermal capillaries, and AQP-3 was abundant in basal epidermal layers. Both AQP displayed several times higher expression in embryonic than in adult skin. TEWL was highest at embryonic day 18 (E18) (133 +/- 18 g/m2h) and lower at E20 (25 +/- 1 g/m2h) and P4 (9 +/- 2 g/m2h). Skin hydration measured as skin electrical capacitance paralleled TEWL, being highest in fetal skin (794 +/- 15 pF at E18) and decreasing to 109 +/- 11 pF at E20 and to 0 +/- 0 pF at P4. We conclude that, as in infants, water loss through the skin of rats decreases markedly with maturation during the perinatal period. The expression and cellular localization of the AQP are such that they might influence skin hydration and water transport and contribute to the high losses of water through the immature skin.
The interaction of small phospholipid vesicles with well-characterized surfaces has been studied to assess the effect of the surface free energy of the underlying monolayer on the formation of phospholipid/alkanethiol hybrid bilayer membranes (HBMs). The surface free energy was changed in a systematic manner using single-component alkanethiol monolayers and monolayers of binary mixtures of thiols. The binary surfaces were prepared on gold by self-assembly from binary solutions of the thiols HS-(CH(2))(n)()-X (n = 11, X = CH(3) or OH) in THF. Surface plasmon resonance (SPR), electrical capacitance, and atomic force microscopy (AFM) measurements were used to characterize the interaction of palmitoyl,oleoyl-phosphatidylcholine (POPC) vesicles with the surfaces. For all surfaces examined, it appears that the polar part of surface energy influences the nature of the POPC assembly that associates with the surface. Comparison of optical, capacitance, and AFM data suggests that vesicles can remain intact or partially intact even at surfaces with a contact angle with water of close to 100 degrees. In addition, comparison of the alkanethiols of different chain lengths and the fluorinated compound HS-(CH(2))(2)-(CF(2))(8)-CF(3) that characterize with a low value of the polar part of the surface energy suggests that the quality of the underlying monolayer in terms of number of defects has a significant influence on the packing density of the resulting HBM layer.
BACKGROUND: Animal models are important tools for studies in skin physiology and pathophysiology. Due to substantial differences in skin characteristics such as thickness and number of adnexa, the results of animal studies cannot always be directly transferred to the human situation. Therefore, transplantation of human skin on to SCID (severe combined immunodeficiency) mice might offer a promising tool to perform studies in viable human skin without the direct need for human volunteers. OBJECTIVES: To characterize the physiological and anatomical changes of a human skin transplant on a SCID animal host. METHODS: In this study human skin was transplanted on to 32 SCID mice and followed for 6 months. Barrier function was assessed by transepidermal water loss (TEWL; tewametry) and moisture content of the stratum corneum was studied by measurement of electrical capacitance (corneometry). RESULTS: The results showed considerable deviations of TEWL values and skin hydration between the grafts and human skin in vivo. The human skin showed epidermal hyperkeratosis and moderate sclerosis of the corium 4 and 6 months after transplantation on to SCID mice. CONCLUSIONS: Our results indicate that human skin does not completely preserve its physiological and morphological properties after transplantation on to SCID mice. Therefore, results from experiments using this model system need to be discussed cautiously.
The differentiation and barrier formation of cultured composite skin grafts (CSGs) were assessed by histology and measurements of surface electrical capacitance (SEC) in vitro and in vivo. Keratinocytes cultured on the surface of acellular dermis were lifted to the air-liquid interface and analyzed for 30 days in vitro. Initially, SEC measurements of CSGs (n = 11) were high but quickly dropped between days 4 and 6 and remained steady for 30 days, indicating barrier formation by the epidermis. Histology of the CSGs (n = 6) demonstrated stratification of the epidermal cells and partial formation of the stratum corneum by day 3 that was complete by day 7. CSGs (n = 5) were transplanted to athymic mice, where they formed a stratified and differentiated epidermis. SEC measurements of CSGs remained low after transplant, suggesting that exposure to the air-liquid interface improved the maturation of CSGs in vitro prior to transplant.
The study described in this paper constitutes a practical assay system to evaluate in vivo drug penetration using two complementary non-invasive methods. An electrical capacitance test was first applied to the skin on the forearm to evaluate the hydration of the skin, and check the integrity of the stratum corneum. In the first step, the percentage absorption was measured using an occlusive and difference method; following benzophenone-3 application any residual formulation was washed off and the amount removed analyzed. In the second step, the tape stripping method-a useful procedure for selectively removing the skin's outermost layer, the stratum corneum, and measuring the stratum corneum adsorption-was performed. Under these conditions the human skin permeation of this UV-filter over four hours was near to 35% of the applied dose with the occlusive method. The amount of topically applied benzophenone-3 found in the stratum corneum after 30 min exposure using the stripping procedure was evaluated at 4% to the applied dose.
The silk weave spun by hornet larvae before undergoing pupal metamorphosis is composed of fibers and sheets, both containing symbiotic bacteria. The bacteria are secreted from the silk gland and are glued to the secreted silk, which is made up of amino-acid polymers. In the dark, it possesses at first an electric current amounting to several hundred nanoamperes (nA) (i.e., a thermoelectric property), and a high electric capacitance of up to several milliFarads (mF). This electrical charge is used gradually by the developing pupa. The symbiotic bacteria penetrate through slits in the coat of the silk fibers to the core or into pockets in the sheets, where they gradually digest parts of the silk weave, thereby nullifying its mechanical properties and facilitating in due time the egress of the imago from the puparium.
BACKGROUND: Capacitively coupled electric stimulation has been successfully used in the treatment of bone nonunions and to effect spinal fusions. However, the pathway of biologic events whereby this is accomplished has not been fully elucidated. To determine whether bone morphogenetic proteins (BMPs) could be involved, the effect of electrical stimulation on BMP gene expression was investigated. METHODS: Postconfluent cultures of MC3T3-E1 bone cells were exposed to a series of capacitively coupled signals in which the duration, amplitude, frequency, and duty cycle were sequentially and systematically varied. The cellular response was measured by quantifying the mRNA levels of BMP-2 through BMP-8, as well as the BMP antagonists gremlin and noggin, with use of reverse transcription followed by real-time quantitative polymerase chain reaction. BMP-2 protein was measured by enzyme-linked immunosorbent assay, and alkaline phosphatase activity was measured by a specific colorimetric assay. RESULTS: The results showed that BMP-2 through BMP-8, gremlin, and noggin were all normally expressed by MC3T3-E1 cells, and could be significantly up-regulated by specific and selective capacitively coupled electric fields (p < 0.05). However, mRNA expression for BMP-2, 4, 5, 6, and 7 was consistently up-regulated several times higher than that for BMP-3 and BMP-8, gremlin, and noggin under identical conditions. Concomitantly, BMP-2 protein production and alkaline phosphatase activity were both significantly increased in the same electrically stimulated cultures (p = 0.001 and p < 0.01, respectively). CONCLUSIONS: These data clearly show that our optimal capacitively coupled signal (60 kHz, 20 mV/cm at a 50% duty cycle for twenty-four hours) can specifically, selectively, and simultaneously up-regulate the expression of a number of osteoinductive BMPs; other BMPs and antagonists are only moderately affected.
1. We have investigated the granule size distributions in human and horse eosinophils by time-resolved patch-clamp capacitance measurements. 2. During exocytosis of single granules the electrical capacitance of the plasma membrane increases in discrete steps. The steps in horse cells are about six times larger than those in human cells in accordance with the difference in granule size. 3. In both species a multimodal capacitance step size distribution is observed with a first peak at 6-7 fF corresponding to granules with a diameter of about 450-500 nm and a surface area of about 0.7 microns2, which we call the unit granule. The other peaks in the distributions correspond to multiples of the surface area of these units. 4. These results show that the larger granules are formed by fusion of several unit granules and the final size of mature granules is determined by the number of units allowed to fuse with each other. Whereas in human eosinophils most granules consist of one or two units, most granules of horse eosinophils are formed by fusion of seven to fifteen units. 5. The intracellular fusion events associated with vesicular traffic are believed to occur constitutively. In contrast, our results indicate that a cellular mechanism exists which regulates the size of the mature granules by determining the number of units allowed to fuse with each other. In view of our recent report that granule-granule fusion can be activated by GTP gamma S, this regulation may possibly involve GTP-binding proteins.
Antidiuretic hormone (ADH) increased the electrical capacitance of apical membrane of the toad bladder; this effect was modulated by the osmotic gradient across the tissue. Capacitance was measured from the transepithelial voltage response to constant-current pulses using bladders depolarized with KCl-sucrose serosal solution to reduce basolateral resistance and with Na-free mucosal solution to increase apical membrane resistance. Addition of ADH (20 mU/ml) increased capacitance by 28 +/- 9% (mean +/- SD) in the absence and by 8 +/- 3% in the presence of an osmotic gradient (200 mosM, mucosal side hypotonic). With bladders stimulated in the absence of an osmotic gradient, rapidly imposing a gradient resulted in a peak rate of water flow that declined to 40% of the peak value after 15-20 min. ADH-dependent capacitance also decreased with a similar time course. Removal of ADH reversed the capacitance change (t1/2 = 10-15 min), but the reversal was slower than the decline in water flow to basal levels (t1/2 less than 5 min). Colchicine and cytochalasin B also inhibited the ADH-induced capacitance increase. The capacitance change was also inhibited when the mucosal solution was made hypertonic with raffinose. The results are interpreted within the framework of a previously proposed model of ADH-stimulated water transport in which cytoplasmic vesicular structures fuse with the apical plasma membrane.