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PubMed1991

Can transcutaneous recordings detect gastric electrical abnormalities?

The ability of transcutaneous recordings of gastric electrical activity to detect gastric electrical abnormalities was determined by simultaneous measurements of gastric electrical activity with surgically implanted serosal electrodes and cutaneous electrodes in six patients undergoing abdominal operations. Transient abnormalities in gastric electrical activity were seen in five of the six patients during the postoperative period. Recognition of normal gastric electrical activity by visual analysis was possible 67% of the time and with computer analysis 95% of the time. Ninety four per cent of abnormalities in frequency were detected by visual analysis and 93.7% by computer analysis. Abnormalities involving a loss of coupling, however, were not recognised by transcutaneous recordings. Transcutaneous recordings of gastric electrical activity assessed by computer analysis can usually recognise normal gastric electrical activity and tachygastria. Current techniques, however, are unable to detect abnormalities in electrical coupling.

Diagnosis, Computer-Assisted↗
PubMed1990

Electrical properties of canine subendocardial Purkinje fibers surviving in 1-day-old experimental myocardial infarction.

The passive electrical properties of subendocardial Purkinje fibers surviving in infarcted regions of canine ventricle 24 hours after coronary ligation were studied by using microelectrode techniques and cable theory. In normal hearts, cells within the subendocardial Purkinje fiber strands were found to be well coupled to each other but electrically isolated from neighboring myocardium. Voltage response to intracellular current injection was consistent with one-dimensional cable behavior and yielded estimates of passive electrical properties in general agreement with previous work on free-running Purkinje strands (membrane length constant, 1.2 +/- 0.1 mm; membrane time constant, 7.3 +/- 0.8 msec; input resistance, 67.4 +/- 7.4 K omega; membrane resistance, 8.2 +/- 0.7 K omega.cm; axial resistance, 0.52 +/- 0.06 M omega/cm; membrane capacitance, 960 +/- 102 nF/cm) (n = 21). On the day after coronary ligation, subendocardial Purkinje fiber action potentials were prolonged and slightly depolarized. Significant increases were measured in input resistance (+40.5%), membrane resistance (+43.9%), and axial resistance (+47.5%), whereas membrane capacitance was found to be significantly decreased (-24.3%) (n = 19). Conduction velocity, membrane length constant, membrane time constant, and the time constant and capacitance for the foot of the action potential remained unchanged. These results are consistent with electrical uncoupling between adjacent cells, which will increase internal resistivity, accompanied by changes in cellular phospholipid content, which can increase membrane resistance and alter membrane capacitance. Alternatively, the results can be explained by a simple model in which the apparent electrical structure is altered by changes in electrical coupling alone, with specific electrical properties remaining constant. Although the mechanisms underlying the observed changes remain uncertain, the present study indicates that myocardial infarction is associated with alterations in the passive electrical structure of surviving subendocardial Purkinje fibers, which, together with changes in action potential configuration, may provide a substrate for the generation of ventricular arrhythmias 24 hours after coronary ligation.

Action Potentials↗
PubMed2005

Nifekalant hydrochloride suppresses severe electrical storm in patients with malignant ventricular tachyarrhythmias.

BACKGROUND: Some patients with an implantable cardioverter-defibrillator (ICD) suffer from burst of inappropriate multiple discharges (severe electrical storm), and because the current therapeutic options are limited, the effect of nifekalant hydrochloride, a new class III drug, on severe electrical storm was investigated in the present study. METHODS AND RESULTS: Ninety-one consecutive patients treated with ICD were included in the study (M 70; mean age 58 years; left ventricular ejection fraction 45+/-15%). Severe electrical storm was defined as more than 10 ICD discharges within 1 h. During a mean follow-up period of 30+/-13 months, 41/91 (45%) patients had appropriate ICD therapy for arrhythmias and severe electrical storm occurred in 11 of them (12%) at 20+/-18 months after ICD implantation. The mean number of ICD discharges/h during severe electrical storm was 18+/-12. In 4 of 10 patients, severe electrical storm was successfully suppressed by a combination of deep sedation and beta-blocking agent; 6 other patients were refractory to this treatment, but severe electrical storm was successfully suppressed by intravenous administration of nifekalant hydrochloride with no adverse effects. CONCLUSIONS: Nifekalant hydrochloride is an effective and safe treatment for severe electrical storm.

Adolescent↗
PubMed2005

Electrical coupling between interneurons with different excitable properties in the stratum lacunosum-moleculare of the juvenile CA1 rat hippocampus.

Electrical coupling among GABAergic interneurons is believed to play an essential role in shaping synchronized brain network activity related to cognition and behavior. We have studied the rules governing the electrical coupling between hippocampal interneurons located in stratum lacunosum-moleculare of the CA1 hippocampus. The most frequently recorded interneuron subtype had short multipolar dendrites and a dense local axonal arborization, typical of neurogliaform cells. Electrical excitability in this class of interneurons was heterogeneous. Although injection of small current steps evoked late spiking, larger steps triggered different types of firing patterns. Trains of action potentials ranged from clearly adapting to highly irregular, with clustered or mostly regular spikes. Electrotonic and action potentials could be propagated to the coupled cells; the coupling coefficient for electrotonic signals was 0.035, which compared with 0.005 for action potentials. Electrical coupling was reversibly blocked by application of carbenoxolone. Multiple simultaneous recordings indicated that interneurons with similar and different firing patterns were electrically coupled. This visual impression was quantitatively confirmed by principal component analysis applied to variables related to membrane excitability. In fact, the probability of finding electrically coupled neurons in our sample was not dependent on the excitable properties of the cells tested and was approximately 0.34. The presence of diffuse electrical coupling among hippocampal interneurons of stratum lacunosum-moleculare with different excitability is a novel finding with important implications. For example, the promiscuity of electrical connections may endow inhibitory networks with a large degree of flexibility and regulate the computational power of the hippocampus during different synchronized states.

Action Potentials↗
PubMed2006

Sequence and time dependence of transfection efficiency of electrically-assisted gene delivery to tumors in mice.

Electrically-assisted gene delivery is a non-viral gene delivery technique, using application of square wave electric pulses to facilitate uptake of plasmid DNA into the cells. Feasibility and effectiveness of this method in vivo was already demonstrated, elaborating on pulse parameters and plasmid construction. However, there were no studies performed on sequencing and timing of plasmid DNA injection into the tumors and application of electric pulses. For this purpose we measured luciferase expression in two tumor models (LPB fibrosarcoma, B16F1 melanoma) after electrically-assisted gene delivery at varying time intervals between the pCMV-Luc plasmid injection and electroporation. Expression of luciferase was determined by measurement of its activity using luminometer. The results demonstrated that pCMV-Luc plasmid has to be injected before the application of electric pulses, since no measurable expression was detected in the tumors when pCMV-Luc plasmid was injected after electroporation of tumors. In both tumor models the highest transfection efficiency was obtained when pCMV-Luc plasmid was injected not less than 5 minutes but also not more than 30 minutes before the application of electric pulses. The results also demonstrated variability in the transfection efficiency depending on the tumor model. High expression was obtained in B16F1 tumor model (approximately 5500 pg luc/mg tumor) and lower in LPB fibrosarcoma (approximately 200 pg luc/mg tumor). In conclusion, our results demonstrate that regardless of the susceptibility of the tumors to electrically-assisted gene delivery, the best timing for pCMV-Luc plasmid is between 30 to 5 minutes prior to the application of electric pulses to the tumors.

Animals↗
PubMed1998

Increased levels of free fatty acids in fasted mice stimulate in vivo beta-cell electrical activity.

The electrical activity of pancreatic beta-cells in 48-h fasted mice has been recorded in vivo. Their electrical activity is exceedingly high at low levels of blood glucose when compared with control animals. For example, at a blood glucose concentration of 4.5 mmol/l, at which beta-cells are permanently hyperpolarized in control animals, fasted animals show continuous spiking activity. In fasted animals, hyperpolarization only occurs at glycemias below 2.2 mmol/l. As in fed animals, the electrical activity in fasted mice can be decreased or suppressed by the injection of diazoxide, indicating the participation of K(ATP) channels. The treatment of fasted animals with nicotinic acid, an inhibitor of lipolysis, produces a decrease in the levels of free fatty acids (FFAs) and a decrease in electrical activity, thereby restoring the dose-response curve for glucose in fasted animals to values close to those found in fed animals. Conversely, the injection of palmitic acid produces an increase in electrical activity without a change in blood glucose. These results point to FFAs as important regulators of electrical activity during fasting in vivo. They also indicate a dissociation of electrical activity and insulin release in fasted animals, since an increase in electrical activity is not associated with increased insulin secretion.

Animals↗
PubMed2001

[Electric pulse mediated high efficient gene transfer].

OBJECTIVE: To study gene transfer mediated by electric pulse and optimize the parameters of electric pulse in vivo. METHODS: 10 micrograms plasmid pcD2/LacZ was injected into the quadriceps of 220 Kunming mice. One to two minutes after the DNA injection electric pulse with different parameters was given to the injection site. Three days after, activity of beta-galactosidase was measured, and the expression of Laz2 gene in muscle was determined by histochemical staining. RESULTS: The activity of beta-galactosidase in electric pulse group (131.6 U/mg +/- 86.6 U/mg protein) was 30 fold higher than that in direct injection group (4.9 U/mg +/- 1.0 U/mg protein) (P < 0.05). Histochemical analysis of muscles injected with a LacZ expression plasmid also showed that in vivo electric pulse increased both the number of positively stained muscle fibers and the density of staining. When the electric pulse was with the parameters of 200 V/cm, 40 ms, 6 pulses and 1HZ, maximal gene expression was achieved. CONCLUSION: Electric pulse, with optimal parameters, increases gene expression. Electric pulse makes much more gene expression than mere intramuscular DNA injection.

Animals↗
PubMedDate not supplied

The effect of different frequency electrical acu-stimulation on gastric myoelectrical activity in healthy subjects.

BACKGROUND/AIMS: Acupuncture has been used to treat gastrointestinal symptoms in oriental countries for many years. The underlying mechanism is still not fully understood. METHODOLOGY: Fifteen healthy male volunteers were enrolled into this study. A cutaneous electrogastrography recording was obtained. Two frequencies (2 Hz and 100 Hz) of electrical stimulation were applied to Zusnali or Shousanli point in different sessions. Another non-acu-point (2 cm lateral to Zusanli) without electrical stimulation was used for a control study. RESULTS: There was a significant increase in the percentage of normal frequency during 2 Hz of electrical stimulation on Zusnali (baseline vs. acupuncture, 82.49 +/- 12.87% vs. 93.18 +/- 8.40%, p < 0.01). The percentage of normal frequency did not change significantly, during or after acupuncture, with 100 Hz of electrical stimulation on Zusnali, or 2 Hz and 100 Hz of electrical stimulation on Shousanli. In addition, the percentage of tachygastric frequency and power ratio also changed significantly during 2 Hz of electrical stimulation on Zusnali. However, the change in the percentage of bradygastria and dominant frequency was not statistically significant among all five study sessions during each stage. CONCLUSIONS: The results of this study demonstrated that electrical stimulation, with a frequency of 2 Hz, on Zusanli might enhance the regularity of gastric myoelectrical activity. The effect of acupuncture on gastric myoelectrical activity was acu-point-specific, and that effect was observed with 2 Hz but not 100 Hz electrical stimulation.

Adult↗
PubMed2006

[Electrical storms in patients with implantable cardioverter-defibrillator: incidence and clinical management].

BACKGROUND: Electrical storm in implantable cardioverter-defibrillator (ICD) recipients is a dramatic experience for the patient and a hard emergency for the cardiology team. The aim of our study was to evaluate the incidence and the clinical significance of electrical storm in a standard population of ICD patients. METHODS: We considered retrospectively 262 consecutive ICD patients (86% males, mean age 65+/-10.7 years). Patients were divided into three groups: 88 patients without appropriate ICD therapy (group A); 140 patients with isolated ICD therapies (group B); 34 patients with electrical storm episodes (> or = 3 appropriate ICD therapies/24 h) (group C). Survival study (endpoint death) was performed for each group of patients. RESULTS: There was no difference in age, sex, heart disease, ejection fraction or NYHA functional class among the three groups. ICD implant was performed for secondary prevention in 79% of group C patients and in 74.3 % of group B patients, but only in 39.8 % of group A patients (p < 0.0001). Mean follow-up was 31.1+/-29.8 months in group A, 55.1+/-38 months in group B, and 71.1+/-51.7 months in group C. The endpoint was reached by 16 patients (18%) of group A, by 53 patients (38%) of group B, and by 20 patients (58%) of group C. Comparison of the survival curves of the three groups did not show significant differences. In group C patients, 54 electrical storm episodes were recorded (mean 1.5/patient). CONCLUSIONS: In our population of ICD patients, we observed electrical storm in 34 patients (12.9%). Survival in group with episodes of electrical storm was comparable to patients without electrical storm; thus, in our experience, electrical storm could not represent a negative prognostic factor.

Aged↗
PubMed1980

Structural analysis of electrical properties of cells and tissues.

Most cells and tissues have electrical properties relevant to their natural function. Most cells and tissues have rather complex structure, consisting of folding and invaginating membranes and specialized connections and organelles. The localization of electrical properties is particularly important, since each of the complex structures must be expected to have a specific role in the electrical function of the tissue. The structural analysis of electrical properties consists then in the measurements of the electrical properties of the individual components of the tissue or cell. The structural analysis proceeds by a qualitative analysis of the topology of the preparation, followed by quantitative measurements of the morphometric parameters, the surface, and volume of the relevant structures. A theoretical analysis is performed to determine the electrical properties expected from such a structure. Measurements of natural and induced electrical properties are then made. Comparison of the observed electrical properties with those predicted allows determination of the properties of individual components of the tissue. In this manner the role of individual membrane systems in the function of both skeletal muscle and the lens of the eye has been determined.

Cell Membrane Permeability↗
PubMed1980

Electric potential at regions near the two specific thiols of heavy meromyosin determined by the fluorescence quenching technique. I. Effect of ATP.

Electric potentials at regions near the two specific thiol groups, SH1 and SH2, of the heavy meromyosin (HMM) molecule were studied by the fluorescence quenching technique. The effects of binding of ATP to HMM upon the electric potentials were also studied. N-(p(2-Benzimidazolyl)phenyl)maleimide (BIPM) was used as a thiol-directed fluorescent reagent. Prior to the labeling of SH2 with BIPM, the SH1 group was blocked with N-ethylmaleimide (NEM). Iodide ions (I-), thallium ions (Tl+), and acrylamide were used as quenchers of fluorescence. The sign of the electric potential was collectively determined from the dependence of the Stern-Volmer constants upon the ionic strength of solutions. 1. The region near SH1 was at a negative electric potential, whereas the electric potential at the region near SH2 was almost zero. 2. On the addition of ATP, the fluorescence intensity of BIPM bound to SH1 was unchanged, whereas that of BIPM bound to SH2 was greatly decreased to about 50% of the original level. The fluorescence intensity recovered as the added ATP was split into ADP and orthophosphate, and became saturated. The saturated level of the fluorescence intensity was, however, smaller than the original one, due to binding of the produced ADP to HMM. 3. On the addition of ATP, the negative electric potential at the region near SH1 was unchanged, whereas a negative electric potential with large gradient was newly introduced at the region near SH2. The value of the newly introduced electric potential was calculated on the basis of various assumptions. These results are discussed in connection with the functions of myosin.

Acrylamides↗
PubMed1995

Electrical activity and calcium influx regulate ion channel development in embryonic Xenopus skeletal muscle.

The development of electrical excitability involves complex coordinated changes in ion channel activity. Part of this coordination appears to be due to the fact that the expression of some channels is dependent on electrical activity mediated by other channel types. For example, we have previously shown that normal potassium current development in embryonic skeletal muscle cells of the frog Xenopus laevis is dependent on sodium channel activity. To examine the interrelationships between the development of different ionic currents, we have made a detailed study of electrical development in cultured Xenopus myocytes using whole-cell patch-clamp recording. The initial expression of potassium, sodium, and calcium currents is followed by a brief period during which the densities of potassium currents decrease, while at the same time sodium and calcium current densities continue to increase, which may increase electrical excitability during this time. The normal developmental increase in both potassium and sodium currents is inhibited by the sodium channel blocker tetrodotoxin, suggesting that electrical activity normally stimulates the expression of both these currents. These effects of electrical activity appear to be mediated via activation of voltage-gated calcium channels. We suggest that the developmental acquisition of sodium and calcium channels by these cells, possibly coupled with a transient decrease in potassium current density, lead to an increase in electrical excitability and calcium entry, and that this calcium entry provides a critical developmental cue controlling the subsequent development of mature electrical properties.

Animals↗
PubMed1996

Electrical alternans and the onset of rate-induced pulsus alternans during acute regional ischaemia in the anaesthetised pig heart.

OBJECTIVES: Electrical alternans and mechanical alternans are both associated with cardiac ischaemia and in the case of electrical alternans there is a strong link with serious ventricular arrhythmia. We elected to investigate the relationship between electrical and mechanical alternans in control and acutely ischaemic myocardium in the intact porcine heart to determine the nature of their interaction and in particular to determine if abnormal mechanical events play a role in arhythmogenesis as has been suggested in non-ischaemic preparations. METHODS: We used rapid atrial pacing to induce regional mechanical alternans and pulsus alternans before and then at 5-min intervals after the onset of acute ischaemia induced by a 30-min ligation of a diagonal branch of the left anterior descending artery. Regional mechanical activity is measured with epicardial tripodal strain gauges and regional electrical activity is measured using suction-based monophasic action potential electrodes. To test whether alternate stretching of ischaemic segments during pulsus alternans contributed to electrical alternans we simulated pulsus alternans by clamping the proximal aorta on alternate beats. RESULTS: In control areas there was a constant discordant relationship between peak systolic pressure during alternans and action potential duration. In contrast, the ischaemic areas showed electromechanical alternans that was most frequently concordant. Clamping the proximal aorta on alternate beats produced an electrical alternans in control areas but not in the ischaemic area. CONCLUSIONS: Pulsus alternans during acute ischaemia is associated with electrical alternans that can be out of phase in control and ischaemic areas. This could increase electrical dispersion which may be pro-arrhythmic.

Action Potentials↗
PubMed1997

Hippocampal electrical activity and behavior in the rabbit.

Different approaches to the study of the relationship between hippocampal electrical activity and behavior have shown that hippocampal EEG varies according to different behavioral aspects. In particular, a rhythmic slow activity (RSA, Theta rhythm) can be recorded during voluntary movements and to a lesser degree during immobility. In laboratory experiments, we tried to evaluate the influence on the hippocampal EEG of external stimuli evoking emotional or cognitive responses. Similar electrical responses were observed during animal hypnosis and in the presence of threatening stimuli, while some electrical parameters, such as frequency and rhythmicity, varied according to the nature of the stimulus. In order to have greater and clearer information, we adopted a neuro-ethological approach ch. which allowed us to classify behavior into several categories and to record the hippocampal EEG during natural behavior. The influence exerted on hippocampal electrical activity by novel stimuli and the electrical profiles recorded during exploratory behavior or alert or quiet immobility allowed us to classify the hippocampal EEG on the basis of frequency and rhythmicity. Moreover, the study of social behavior showed that the variations of the electrical parameters of the hippocampal activity depended on the characteristics of the stimulus and that typical electrical profiles could be observed in immobile or motor activities caused by specific stimuli. Socially dominant and subordinate rabbits could also be distinguished on the basis of hippocampal electrical parameters.

Animals↗
PubMed1998

Diversity of sexual dimorphism in electrocommunication signals and its androgen regulation in a genus of electric fish, Apteronotus.

Gymnotiform electric fish emit an electric organ discharge that, in several species, is sexually dimorphic and functions in gender recognition. In addition, some species produce frequency modulations of the electric organ discharge, known as chirps, that are displayed during aggression and courtship. We report that two congeneric species (Apteronotus leptorhynchus and A. albifrons) differ in the expression of sexual dimorphism in these signals. In A. leptorhynchus, males chirp more than females, but in A. albifrons chirping is monomorphic. The gonadosomatic index and plasma levels of 11-ketotestosterone were equivalent in both species, suggesting that they were in similar reproductive condition. Corresponding to this difference in dimorphism, A. leptorhynchus increases chirping in response to androgens, but chirping in A. albifrons is insensitive to implants of testosterone, dihydrotestosterone or 11-ketotestosterone. Species also differ in the sexual dimorphism and androgen sensitivity of electric organ discharge frequency. In A. leptorhynchus, male discharge at higher frequencies than females, and androgens increase electric organ discharge frequency. In A. albifrons, males discharge at lower frequencies than females, and androgens decrease electronic organ discharge frequency. Thus, in both chirping and electric organ discharge frequency, evolutionary changes in the presence or direction of sexual dimorphism have been accompanied and perhaps caused by changes in the androgen regulation of the electric organ discharge.

Androgens↗
PubMed2005

Electrosensory interference in naturally occurring aggregates of a species of weakly electric fish, Eigenmannia virescens.

The detection and identification of behaviorally relevant signals in the presence of competing signals in the environment is a major challenge of animal sensory systems. In weakly electric fish such as Eigenmannia virescens, the interactions between the autogenous electric field and the electric fields of nearby conspecifics can have profound effects on the perception of other behaviorally relevant electrosensory information. To better understand the natural signals that the nervous system of Eigenmannia experiences during the processing of electrosensory information, we examined the electrosensory milieu of Eigenmannia in the wild and in the laboratory. Recordings of the electric fields of Eigenmannia were made in 'black' and 'white' waters near the Napo River in eastern Ecuador. Fourier analysis revealed that Eigenmannia typically experience the electric fields of three to five conspecifics during the day and night in each habitat. The median difference in electric organ discharge frequencies between nearby Eigenmannia during the day was 23 Hz in black water habitats, 41 Hz in white water, and 37 Hz at night in both habitats: these signals are known to activate tuberous electroreceptors and downstream CNS circuits. There was no correlation between the number of individual Eigenmannia detected at recording sites and electric organ discharge frequencies. Further, Eigenmannia apparently do not maximize the frequency differences between conspecifics. In laboratory studies fish were preferentially observed in aggregates of two fish or more. Aggregate sizes observed in the laboratory were similar to those in the wild.

Animal Communication↗
PubMed1997

Injury by electrical forces: pathophysiology, manifestations, and therapy.

The pathogenesis and pathophysiologic features of electrical injury are more complex than once thought. The relative contributions of thermal and pure electrical damage depend on the duration of electric current passage, the orientation of the cells in the current path, their location, and other factors. If the contact time is brief, nonthermal mechanisms of cell damage will be most important and the damage is relatively restricted to the cell membrane. When contact time is much longer, however, heat damage predominates and the whole cell is affected directly. These parameters also determine the anatomic tissue distribution of injury. Damage by Joule heating is not known to be dependent on cell size, whereas larger cells are more vulnerable to membrane breakdown by electroporation. Cells do survive transient plasma membrane rupture under appropriate circumstances or if therapy is instituted quickly. If membrane permeabilization is the primary cellular pathologic condition, then injured tissue may be salvageable and the challenge for the future is to identify a technique to reseal the damaged membranes promptly. Present standards of care for electrical injury require a fully staffed and well-equipped intensive care unit, available operating suites, and the availability of the full range of medical specialists. Major teaching hospitals with burn centers may be the ideal setting for the treatment of an electrical trauma victim. After the initial resuscitation, efforts are directed primarily towards preventing additional tissue loss mediated through the compartment syndrome, compressive neuropathies, or the presence of necrotic tissue. Renal and cardiac failure caused by the release of intracellular muscle contents into the circulation must be prevented. Attention can then be directed towards maximizing tissue salvage and preventing late skeletal and neuromuscular complications. Reconstructive procedures that transfer healthy tissue from a distance are necessary to optimize the functional value of the remaining tissue. Finally, unless the patient is rehabilitated psychologically, the real benefit from other sophisticated care will not be fully realized. These goals are important throughout the acute care of the patient. In the future, new guidelines for treating electrical trauma will be based on a clearer understanding of the relevant pathophysiologic features. These strategies will rely on improved diagnostic imaging and on reversing the fundamental problem of cell membrane damage. Moreover, complex biochemical and organ system pathophysiologic interactions will require careful management. If successful, research efforts presently underway should improve the prognosis of victims after electrical trauma.

Burns, Electric↗
PubMed2000

Relation between tissue structure and imposed electrical current flow in cervical neoplasia.

BACKGROUND: When an electrical potential is applied to human tissue, the pattern of the resulting current flow is determined by the shapes, arrangements, and internal structure of the tissue cells. By measurement of the electrical current patterns over a range of frequencies, and use of an inverse modelling procedure, electrical variables describing the tissue structure can be calculated. We used this method to develop a screening technique for the detection of cervical precancers. METHODS: We used a pencil probe (diameter 5 mm) to measure electrical impedance spectra from eight points on the cervix in 124 women with abnormal cervical smears. Variables that should be sensitive to the expected tissue changes were calculated. These were compared with the colposcopic results. FINDINGS: The measured electrical impedance changes were those predicted on the basis of the expected tissue structures. Measurements made on normal squamous tissues were well separated from those made on precancerous tissues. We constructed receiver-operating-characteristic curves, comparing measurements made on normal tissue and that showing cervical intraepithelial neoplasia grade 2/3; the area under the curve was 0.951. These groups of women could be separated with a sensitivity of 0.92 and a specificity of 0.92. INTERPRETATION: Characteristics of the electrical impedance spectra of tissues can be explained by changes in cell arrangements (layering) and in the size of the nuclei. This relation opens the way to deriving tissue structure from electrical impedance spectral measurements. We show that this approach can be used to give good separation of normal and precancerous cervical tissues.

Biopsy↗