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At least 667 records · Page 37Linked to original sources
PubMed1999

Double-phase 99mTc-sestamibi scintimammography and trans-scan in diagnosing breast cancer.

UNLABELLED: The goal of our study was to assess the value of both scintimammography with 99mTc-sestamibi (SMM) and trans-scan (T-scan) in detecting breast cancer. METHODS: A total of 121 women were evaluated by palpation, mammography, SMM and T-scan. SMM was performed in the prone, breast dependent position. Immediate and delayed views (double-phase) were obtained. T-scan is a new breast imaging method that maps noninvasively the distribution of tissue electrical impedance and capacitance. RESULTS: SMM had 88.9% sensitivity, 88.4% specificity and 88.4% accuracy in detecting breast cancer. SMM had 100% sensitivity in detecting breast tumors >1 cm and only 66% sensitivity in detecting tumors <1 cm. T-scan had 72.2% sensitivity and 67% specificity in detecting breast cancer. It detected one more breast cancer than SMM, at the expense of 27 additional false-positive results. CONCLUSION: Double-phase SMM was sensitive and specific in detecting breast cancer. This method may reduce the rate of negative breast biopsies in tumors >1 cm. T-scan was only moderately accurate in detecting breast cancer. Its addition to SMM did not improve significantly the rate of breast cancer detection. However, because of its complete noninvasiveness, large-scale applicability and low cost, T-scan deserves further refining.

Adult↗
PubMed1992

A three-hour test for rapid comparison of effects of moisturizers and active constituents (urea). Measurement of hydration, scaling and skin surface lipidization by noninvasive techniques.

An in vivo skin test for rapid comparison of the efficacy of moisturizers is introduced. Test substances were applied to flexor side forearm skin, and measurements by non-invasive techniques were performed after 3 h. As indicators of epidermal hydration, the electrical conductance and capacitance were measured. To quantify the effects on scale pattern, D-Squame tapes were scored and the optical transmission measured. Moreover, skin surface lipids resulting from lotion lipids were measured. Lotions and different concentrations of urea could be ranked in a consistent way, viz. untreated skin < vehicle < 3% urea lotion < 10% urea lotion. Urea was concluded to be very potent as a skin humidifier and as a descaling agent, particularly in 10% concentration. Humidity characteristics correlated much better with the concentration of urea than with lipidization of the skin surface due to lotion lipids. A 3-hour test period was sufficient for the evaluation of the effects of moisturizers on both epidermal hydration and scale pattern. With a rapid test method, sources of variation such as diurnal and day-to-day variations, dosage and non-compliance are easily controlled. Further, by using non-invasive methods, the assessment has been rendered objective.

Adult↗
PubMed1990

Effects of oil and water baths on the hydration state of the epidermis.

The effects of bath-oil and tap-water baths were studied by non-invasive bioengineering methods. Measurements of water evaporation, electrical conductance and capacitance demonstrated an increase in cutaneous hydration for 20 min after both types of bath, with the larger increase occurring within the first 10 min. A small but significantly greater amount of water (12-27%) was bound in the skin following use of bath oil. However, measurements of evaporation, conductance and capacitance indicated no clear difference in the skin surface hydration following bath-oil and tap-water baths. Thus, the increase in the water-holding capacity of the skin resulting from bath oil is slight and of no real importance for skin-surface hydration immediately after bathing. There was no difference between 5-min and 20-min baths. Oil baths resulted in an increase in skin-surface lipids lasting at least 3 h, comparable to the effect of traditional moisturizing lotions. This lipidization of the skin surface may have protracted effects. In conclusion, the value of bath oil lies mainly in the general lipidization of the skin with potential improvement in dryness and scaling, i.e. effects which are complex and protracted. The direct hydration of the skin is of short duration and comparable to a tap-water bath. In comparison with lotions, use of an oil bath has the disadvantage that it is not practical for repeated daily treatment over the long period which is necessary for therapy to be effective. The present study on normal skin does not take into account other effects of bathing with or without the addition of oil.

Adult↗
PubMed2005

Electrical impedance scanning of thyroid nodules before thyroid surgery: a prospective study.

BACKGROUND: Electrical impedance scanning (EIS) is a novel imaging technique based on differential electrical conductivity and capacitance of malignant and normal human tissues. The aim of this study was to evaluate the accuracy of EIS in the detection of thyroid malignancies. METHODS: Patients with thyroid nodules scheduled for thyroid surgery were eligible for the study. Enrolled patients underwent EIS with a T-Scan 2000ED. Nodule location, size, and type (cystic vs. solid) measured by ultrasound, cytology results, thyroid conductivity, and capacitance calculated by EIS were recorded. EIS results were interpreted as positive or negative for malignancy and compared with final histopathology results. Study end points included EIS accuracy, sensitivity, specificity, negative and positive predictive values, and false-positive and false-negative rates. RESULTS: Sixty-four patients were enrolled onto the study, and all underwent either lobectomy-isthmusectomy (20%) or total thyroidectomy (80%). The mean tumor diameter was 2.64 +/- 14.8 mm. Thyroid cancers were identified by histology in 30 patients (46.9%). There were 11 false-positive and four false-negative cases. The overall diagnostic accuracy of EIS was 76.6% (49 of 64 correct diagnoses). The sensitivity and specificity of EIS were 86.7% (26 of 30 true positive) and 67.6% (23 of 34 true negative), respectively. The corresponding positive and negative predictive values were 70.3% and 85.2%. CONCLUSIONS: EIS is a potentially useful imaging modality for differentiating thyroid neoplasms. If these results are confirmed in large-scale trials, EIS may be an important part of the evaluation of thyroid nodules.

Adolescent↗
PubMed1989

[Function of the spermatozoal plasma membrane in oocyte fertilization. Cell electrophoresis and immunofluorescence microscopy studies].

The influence of the capacitation on the electric charge of the spermatozoal surface and the unspecific spermatozoon-oocyte-binding are not fully understood up to now. Therefore, human semen samples were divided into two subgroups of spermatozoa by the "swim up" method. Both of the subgroups were examined by means of the micro-electrophoresis and the immunofluorescence technique using antihuman fibronectin antibodies. Cellular electrophoresis: The 2 subgroups of spermatozoa prepared of one semen sample showed a significantly different electrophoretic mobility (EPM) after washing and resuspension in an isotonic glycin-HCl-buffer (pH 2.0). In contrast, after resuspension in Baker's-buffer (pH 7.4) no difference between the 2 subgroups of one semen sample was detectable. The incubation in a medium with Ca++ caused secondly alterations of the EPM with the result of a smaller difference between the two subgroups of spermatozoa. Albumin also modified the EPM of spermatozoa. Immunofluorescence technique: 69 per cent of spermatozoa with a normal shape and only 17 per cent of them exhibiting a pathological shape showed a positive fibronectin-fluorescent-band on the equatorial segment called equatorial fibronectin band (EFB). Spermatozoa separated by "swim up" from semen samples with various semen parameters showed different percentages of spermatozoa with EFB. There was a significant difference between the spermatozoa of the two subgroups after "swim up" concerning EFB.

Electrophoresis↗
PubMedDate not supplied

Flow-pressure looping during plethysmography in wheezy infants.

Marked looping of the expiratory portion of the flow-pressure relationship was noted in some infants during measurements of airway resistance in a whole-body plethysmograph while the respired air was maintained at body temperature and humidity. An investigation of 13 infants who had varying degrees of airway obstruction showed that there was a negative correlation (r = 0.72) between the severity of the looping and specific airway conductance (SGaw). An even stronger correlation (r = 0.85) was found between the tangent of the angle of phase lag between flow and pressure (theta) and the forced expiratory time constant (t) obtained from the partial forced expiratory flow-volume curve. Such a relationship would be predicted from a model in which the lung behaved as a simple electrical resistance-capacitance network during expiration. It is suggested that the looping is the result of small airway closure during expiration in wheezy infants, with a consequent rise in resistance and prolongation of the time constant of the lung.

Airway Resistance↗
PubMed1995

Transducers for foot pressure measurement: survey of recent developments.

Recent advances in the development of transducers for the measurement of vertical and shear forces acting on the plantar surface of the foot are reviewed. Barefoot and in-shoe discrete and matrix transducers are reviewed in terms of structure, operation, performance and limitations. Examples of capacitive, piezo-electric, optical, conductive and resistive types of transducer are presented. Where available, the current clinical status is specified.

Biomechanical Phenomena↗
PubMed1984

Theory and operation of a single microelectrode voltage clamp.

The theory of operation of a discontinuous single-electrode voltage clamp using an ideal microelectrode (infinite response speed) and fixed (current-passing) duty cycle has been previously described. In this paper, the theory is extended by considering a microelectrode which has a finite response speed, by allowing the duty cycle to be variable, and by considering the clamp noise. Formulate are derived for the relationships between the step response, the steady-state error, the steady-state ripple, and the stability, in terms of the cycling frequency, the duty cycle, the open loop gain, and the electrical resistance and capacitance of the microelectrode and the cell membrane. In addition, the amplification of the microelectrode noise by aliasing is analysed, the error due to incomplete decay of the microelectrode voltage is described, and the accuracy of averaging the peak current measurement is established. To achieve the fastest dynamic response and the smallest steady-state error, the cycling period should be made as small as possible, and the open-loop gain should be as large as possible, consistent with stability. Incomplete decay of the microelectrode voltage destabilizes the clamp, and can introduce a significant clamp error. The choice of duty cycle is a compromise between reducing the noise and the step response time while avoiding design problems in the current output circuit. The output noise is amplified by aliasing. It can be minimized for a given output filter cutoff frequency by keeping the cycling frequency as high as possible, and by the use of an anti-aliasing filter whose cutoff frequency must be set for each microelectrode.

Animals↗
PubMed1984

Current-voltage characteristics and self-sustained oscillations in dioleyl phosphate-millipore membranes.

For an artificial membrane prepared by infiltrating dioleyl phosphate (DOPH) into pores of a Millipore filter, we propose a theoretical model for explaining observed data on electric behavior, such as d.c. current-voltage characteristics and self-sustained oscillations of the electric potential. The model consists of a simple electric circuit composed of electric resistances and capacitances as given functions of internal variables which represent conformational states of DOPH molecules and salt concentration inside the pore concerned. The kinetic equations for these variables are the same as those presented previously for describing a phase transition of DOPH. except for a slight modification taking account of effects of salt accumulation inside the pore. The present theory can describe well the I-V hysteresis and various features of spike-like oscillations with long periods of up to a few hours in the absence of external force and also short-period oscillations with periods of the order of 1 s under pressure difference.

Journal Article↗
PubMed1990

Mechanisms that degrade timing information in the cochlea.

Action potentials of cochlear nerve fibers are synchronized to the temporal variations of sounds, but this synchronization is attenuated for high-frequency sounds. In cochleas from a number of vertebrates, the frequency dependence of synchronization can be represented as a lowpass filter process whose order is at least three (Weiss and Rose, 1988a); i.e. at least three first-order kinetic processes may be responsible for the loss of synchronization. In this paper we assess the extent to which calcium processes, that are essential for chemical transmission at the hair-cell neuron junction, contribute to this attenuation of synchronization. We analyze a model of calcium processes in hair cells (Lewis, 1985; Hudspeth and Lewis, 1988a) for sinusoidal receptor potentials. We show that: (1) the relation between the receptor potential and the calcium current, which is nonlinear, acts approximately as a first-order lowpass filter whose cut-off frequency decreases with increasing receptor potential magnitude; (2) the relation between calcium current and calcium-concentration is a first-order, lowpass filter with constant cutoff frequency. These two calcium processes plus the lowpass-filter process resulting from the electrical resistance and capacitance of the hair-cell membrane - which limits the rate at which the receptor potential can change (Weiss and Rose, 1988b) - can account for much, although perhaps not for all, of the loss of synchronization of cochlear nerve fibers.

Acoustic Stimulation↗
PubMed2004

Gallium(III) adsorption on carbonates and oxides: X-ray absorption fine structure spectroscopy study and surface complexation modeling.

Adsorption of Ga on calcite, magnesite, amorphous silica, and manganese oxide as a function of pH and gallium concentration in solution was studied using a batch adsorption technique. Adsorbed complexes of Ga on calcite, magnesite, and delta-MnO2 were further characterized using XAFS spectroscopy. At high surface loadings from supersaturated solutions, Ga is likely to form a polymeric network at the surface (edge- and corner-sharing octahedra). At low surface loadings, Ga presents as isolated octahedra, probably attached to the Me-O sites on the surface, and coordinated by water molecules and hydroxide groups at 1.90-1.94 A. At pH>6, Ga therefore changes its coordination from 4 to 6 when adsorbing from solution (Ga(OH)(-)4(aq)) onto metal surface sites (MeOGa(OH)n(H2O)2-n(5-n), Me = Ca, Mg, or Mn, and n=1 and 2 for carbonate minerals and MnO2, respectively). Because the EXAFS is not capable of seeing hydrogen atoms, the protonation of surface complexes was determined by fitting the experimental pH-dependent Ga adsorption edge. A surface complexation model which assumes the constant capacitance of the electric double layer (CCM) and postulates the formation of positively charged, neutral and negatively charged surface complexes for carbonates, manganese oxide and silica, respectively, was used to describe the dependence of adsorption equilibria on aqueous solution composition in a wide range of pH and Ga concentration.

Adsorption↗
PubMed2005

The role of electrode impedance and electrode geometry in the design of microelectrode systems.

Microelectromechanical systems (MEMS) employing spatially and/or temporally nonuniform electric fields have been extensively employed to control the motion of suspended particles or fluid flow. Design and control of microelectromechanical processes require accurate calculations of the electric field distribution under varying electrolyte conditions. Polarization of electrodes under the application of an oscillating voltage difference produces dynamic electrical double layers. The capacitive nature of the double layers significantly inhibits the penetration of the electric field through the double layer and into the surrounding bulk electrolyte at low frequencies. This paper quantitatively discusses the effect of electrode impedance on the electric field distribution as a function of field frequency, electrolyte composition, and electrode zeta potential in microelectrode systems. The design principles for the electrode geometry and configuration are also discussed in terms of their effects on the electric field magnitude and nonuniformity.

Electrodes↗
PubMed2003

Molecular interactions between DNA and an aminated glass substrate.

With the development of DNA arrays, the immobilization of DNA strands onto solid substrates remains an essential research topic. DNA arrays have potential applications in DNA sequencing, mutation detection, and pathogen identification. DNA bound to solid substrates must still be accessible and retain the ability to hybridize with its complementary strands. One technology to produce these arrays involves linking DNA molecule probes to a silanized substrate in microspot patterns and exposing them to a solution of fluorescently labeled samples of DNA targets. The behavior of both the target and probe DNA and their interactions with each other at the substrate surface, particularly with respect to molecular interactions, are poorly understood at the present time. The objective of this work is to model simply the interface interactions between DNA and glass slides modified with an aminosilane (gamma-aminopropyltriethoxysilane, APTS). In aqueous solutions, DNA behaves as a polyacid over a wide range of pH. A glass substrate treated with APTS is positively or negatively charged, depending on the pH. A model of the surface charge of APTS-treated glass has been developed from results of wetting experiments performed at various pH. It has been demonstrated that the surface charge of APTS-treated glass is well described by a model of constant capacitance of the electrical double layer. A good correlation between experimental data on DNA retention at various pH's and the variation of the surface charge of the APTS-treated glass is obtained. This provides an indication of the role of ionic interactions in the adsorption of DNA molecules onto aminated glass slides.

Adsorption↗
PubMed2002

Surface chemistry and dissolution kinetics of divalent metal carbonates.

A surface complexation model (SCM) for divalent metal carbonates (Ca, Mg, Sr, Ba, Mn, Fe, Co, Ni, Zn, Cd, and Pb) is developed based on new electrophoretic measurements and correlation between aqueous and surface reactions stability constants. This SCM postulates the formation of the following surface species: >CO3H0, >CO3-, >CO3Me+, >MeOH0, >MeO-, >MeOH2+, >MeHCO30, and MeCO3- within the framework of a constant capacitance of the electric double layer. It can be used to describe the surface-controlled dissolution kinetics of divalent metal carbonates and allows determination of the order of dissolution reactions with respect to rate-controlling protonated carbonate surface groups in acid solutions (>CO3H0) and hydrated metal groups (>MeOH2+) in neutral to alkaline solutions. The reaction order with respect to protonated carbonate groups increases from 2 for MnCO3 and ZnCO3 to 4 for NiCO3, whereas for hydrated surface metals, it augments from 2 for ZnCO3 to approximately 4 for MnCO3 and NiCO3. The dissolution rates at 5 < or = pH < or = 8 increase in the order Ni < Mg < Co < Fe < Mn < Zn < Cd < Sr < or = Ca approximately = Ba approximately = Pb and correlate nicely with water exchange rates from the aqueous solution into the hydration sphere of the corresponding dissolved cations. Such a correlation allows the generation for all carbonates of a model describing their dissolution/precipitation kinetics, including the effect of various ligands, provided that rate constants and their activation volumes for water exchange around Me(II)-ligand dissolved complexes are available.

Carbonates↗
PubMed1998

Human perspiration measurement.

We review various methods developed for human perspiration measurement and their physiological applications, with special reference to the performance and application of a new home-made ratemeter and instrumentation with a microscope. Many kinds of humidity sensor based on humidity-sensitive electrical properties have been investigated and placed on the market. Recently a capacitive thin-film humidity sensor was constructed and confirmed to be one of the best humidity sensors for accurately and quickly detecting changes in the relative humidity of gas-flow perfused through a ventilated chamber for human perspiration measurement. In this paper we also introduce a new home-made ratemeter with a capacitive humidity sensor, the electrical output of which is not disturbed by changes in ambient temperature, and new instrumentation for directly observing drops of sweat secreted from eccrine glands in human skin and simultaneously measuring the change in amount of perspiration at the same area of skin. Finally, we review physiological applications of the methods for measuring human palmar perspiration including emotional sweating.

Humans↗
PubMedDate not supplied

Complications of laparoscopic pelvic surgery: recognition, management and prevention.

Laparoscopic surgery has many advantages but it is not without complications. The complexity of the surgery significantly influences the complication rate. Laparoscopic surgeons ought to be aware of the possible complications and how they could be prevented, recognized without delay, and managed safely and efficiently. Important complications include injuries to the vessels, bowel and urinary tract. Incisional hernia ought to be reduced by careful closure of the fascia whenever a trocar > or =10 mm is used at the extraumbilical site. Gas embolism is a rare but potentially life threatening complication. Shoulder pain is a minor complication but is exceedingly common; it is less likely to occur if as much gas as possible is removed at the end of the operation while the patient is still in head down Trendelenburg position. Rare complications include pneumothorax, subcutaneous and pre-peritoneal emphysema, cardiac arrhythmia, nerve injury and venous thrombosis. Laparoscopic surgeons should also understand the principles of electrosurgery and how to avoid complications arising from the use of electrical energy including capacitative coupling, direct coupling and insulation failure.

Blood Vessels↗
PubMed1989

A simple method for the study of scale pattern and effects of a moisturizer--qualitative and quantitative evaluation by D-Squame tape compared with parameters of epidermal hydration.

A new tape (D-Squame tape) made for scale pattern assessments was used to study epidermal effects of an oil-in-water emulsion applied at random to forearm skin of 16 volunteers. The contralateral forearm served as an untreated control. The emulsion was applied twice daily for 7 days. Tapes were assessed visually in a medical viewer, and a special system for measurement of optical transmission of the tapes was established. Visual evaluation showed (Day 7) an altered pattern in nine volunteers with an absence of flakes on the treated side, which was not seen on the control side. The optical transmission of the tapes from the 16 volunteers was significantly increased in samples from the test side (P less than 0.001). One week after cessation of treatment the transmission was still increased (P less than 0.02), and one volunteer presented an altered scale pattern according to visual grading. Measurements of electrical conductance and capacitance, both parameters of epidermal hydration, gave similar results, i.e., increased values on Day 7 and increased conductance 1 week later. Thus, the epidermal effects of the emulsion were protracted. Evaluation of the tape method showed this to be reproducible and valid. The method is easy to use and suited for qualitative and quantitative evaluation of variations in the scale pattern of human skin.

Adult↗
PubMed2002

Effects of membrane potential and sphingolipid structures on fusion of Semliki Forest virus.

Cells expressing the E1 and E2 envelope proteins of Semliki Forest virus (SFV) were fused to voltage-clamped planar lipid bilayer membranes at low pH. Formation and evolution of fusion pores were electrically monitored by capacitance measurements, and membrane continuity was tracked by video fluorescence microscopy by including rhodamine-phosphatidylethanolamine in the bilayer. Fusion occurred without leakage for a negative potential applied to the trans side of the planar membrane. When a positive potential was applied, leakage was severe, obscuring the observation of any fusion. E1-mediated cell-cell fusion occurred without leakage for negative intracellular potentials but with substantial leakage for zero membrane potential. Thus, negative membrane potentials are generally required for nonleaky fusion. With planar bilayers as the target, the first fusion pore that formed almost always enlarged; pore flickering was a rare event. Similar to other target membranes, fusion required cholesterol and sphingolipids in the planar membrane. Sphingosine did not support fusion, but both ceramide, with even a minimal acyl chain (C(2)-ceramide), and lysosphingomyelin (lyso-SM) promoted fusion with the same kinetics. Thus, unrelated modifications to different parts of sphingosine yielded sphingolipids that supported fusion to the same degree. Fusion studies of pyrene-labeled SFV with cholesterol-containing liposomes showed that C(2)-ceramide supported fusion while lyso-SM did not, apparently due to its positive curvature effects. A model is proposed in which the hydroxyls of C-1 and C-3 as well as N of C-2 of the sphingosine backbone must orient so as to form multiple hydrogen bonds to amino acids of SFV E1 for fusion to proceed.

Hydrogen Bonding↗