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At least 757 records · Page 42Linked to original sources
PubMedDate not supplied

Neuronal generators of the visual evoked potentials: intracerebral recording in awake humans.

Flash and pattern reversal visual evoked potentials were recorded in awake patients undergoing stereotactic procedures for severe dyskinetic disorders resistant to medical treatment. The nucleus ventralis lateralis thalami was reached via an occipital approach. VEPs were recorded on the scalp at the entrance of the intracerebral electrode, and serially from sites at different depths. A polarity reversal of the surface recorded wave form took place as the intracerebral electrode was advanced beneath the surface cortical layers. As concerns F-VEPs, most of the scalp activity mirrored the potentials recorded down to the depth of 70-65 mm from the thalamus. The largest amplitude of intracerebral F-VEPs was obtained from recording sites at 50-70 mm from the thalamus, i.e., in the depth of the calcarine fissure. A negative wave, peaking around 47-50 msec, became evident in recording sites at 30-40 mm from the thalamus but vanished as the electrode was advanced farther. In only one patient could we record a small negative wave, peaking at 33 msec, in the vicinity of the corpus geniculatum externum. Furthermore, the oscillatory activity recorded from the scalp appeared to be generated in the cortical layers. PR-VEPs also underwent polarity reversal as the electrode traversed the cortex. PR-VEPs disappeared more superficially than F-VEPs. No PR-evoked activity could be recorded in the vicinity of the corpus geniculatum externum. We conclude that slow and fast components of VEPs recorded from the scalp are entirely generated in cortical layers.

Brain Mapping↗
PubMedDate not supplied

Temporal correspondence of intracranial, cochlear and scalp-recorded human auditory nerve action potentials.

Conventional, vertex-ipsilateral ear records ('A'), as well as 3-channel Lissajous' trajectories (3-CLTs) of auditory brain-stem evoked potentials (ABEPs) were recorded from the scalp simultaneously with tympanic membrane electrocochleograms ('TME') and auditory nerve compound action potentials ('8-AP') recorded intracranially using a wick electrode on the auditory nerve between the internal auditory meatus and the brain-stem. The recordings were made during surgical procedures exposing the auditory nerve. The peak latency recorded from 'TME' corresponded to trajectory amplitude peak 'a' of 3-CLT and to peak 'I' of the 'A' channel ABEP. Peak latency of '8-AP' was slightly longer than the latency of peak 'II' of 'A' when '8-AP' was recorded from the root entry zone and the same or shorter when recorded from the nerve trunk. '8-AP' peak latency was shorter than trajectory amplitude peak 'b' of 3-CLT regardless of where the wick electrode was along the nerve. Peak latencies from all recording sites clustered into two distinct groups--those that included N1 from 'TME,' peak 'I' of the 'A' record and trajectory amplitude peak 'a' of 3-CLT, and those that included the negative peak of '8-AP' and trajectory amplitude peak 'b' of 3-CLT, as well as peak 'II' of the 'A' record, when present. In one case, the latency of peak 'II' and trajectory amplitude peak 'b' was manipulated by changing the conductive properties of the medium surrounding the auditory nerve.(ABSTRACT TRUNCATED AT 250 WORDS)

Acoustic Stimulation↗
PubMed1994

Click-evoked responses from the exposed intracranial portion of the eighth nerve during vestibular nerve section: bipolar and monopolar recordings.

We compare the click-evoked compound action potentials from the exposed intracranial portion of the eighth nerve using bipolar and monopolar recording electrodes in patients undergoing vestibular nerve section. It is assumed that a bipolar recording electrode will only record propagated neural activity in the auditory nerve, whereas a monopolar recording electrode may in addition record electrical activity that is conducted passively to the recording site. The results of the present study confirm that the earliest detectable propagated neural activity in the intracranial portion of the auditory nerve occurs with a latency that is close to that of peak II of the brain-stem auditory evoked potentials, and the results also confirm that the late components in the click-evoked compound action potentials that have been demonstrated previously using the monopolar recording technique represent propagated neural activity in the auditory nerve. The results also indicate that the responses that are recorded by a bipolar recording electrode, when the small tips of which are placed on the eighth nerve when it is relatively dry, represent only small populations of nerve fibers. Even when an attempt is made to align the two tips of a bipolar electrode with the course of the auditory nerve, this type of electrode may record from different populations of nerve fibers.

Acoustic Stimulation↗
PubMed1991

A comparison of extracellular and intracellular recordings from medial septum/diagonal band neurons in vitro.

Firing patterns, action potential characteristics and some active membrane properties of guinea-pig medial septum/diagonal band neurons were studied in an in vitro slice preparation. A comparison was made between several types of cells classified according to either extracellularly recorded (n = 130) or intracellularly recorded (n = 30) electrophysiological characteristics. Using multi-barrel extracellular electrodes, three principal cell types were distinguished: slow rhythmic firing cells (29%), fast rhythmic firing cells (65%) and burst-firing cells (6%). Most slow firing cells could also be distinguished from other cell types by their relatively longer action potential duration and a characteristic cadmium-sensitive "hump" in the repolarization phase of the action potential. These characteristics of slow firing cells matched well with the characteristics of cholinergic, slow afterhyperpolarization cells previously identified with intracellular recordings. The action potential shape, firing rate and firing pattern characteristics of about 60% of extracellularly recorded fast rhythmic firing cells matched those of previously identified non-cholinergic fast afterhyperpolarization cells. The remaining extracellularly recorded, rhythmic firing cells (about 10% of slow firing and 40% of fast firing cells) had a mixture of characteristics which precluded unequivocal classification as to cholinergic or non-cholinergic cell type. Using intracellular recording, the bee venom toxin, apamin, was shown to attenuate the characteristic post spike slow afterhyperpolarization of cholinergic cells and greatly enhanced their firing rate to depolarizing pulses. Apamin often attenuated a smaller and more transient afterhyperpolarization found in identified non-cholinergic cells, but firing rate was increased only slightly. Extracellular recordings from slow and fast rhythmic firing cells in the presence of apamin showed that excitability of slow firing cells was enhanced significantly more than fast firing cells. The apamin data support the hypothesis that extracellularly recorded slow firing cells are cholinergic. We conclude that extracellularly recorded medial septum/diagonal band cells characterized by broad action potentials, slow rhythmic firing under microiontophoresed glutamate and a signature "hump" in the falling phase of the action potential are cholinergic cells. Extracellularly recorded fast rhythmic firing cells with a narrow action potential and no "hump" in the action potential are likely to be non-cholinergic cells. This extracellular electrophysiological "fingerprint" for cholinergic medial septum/diagonal band cells in vitro may now be extended to studies in vivo where controversy remains as to the neurochemical identity of basal forebrain cells involved in control of hippocampal slow rhythmic activity.

Action Potentials↗
PubMed2004

Effects of electrode density and electrolyte spreading in dense array electroencephalographic recording.

OBJECTIVE: High-density EEG recording offers increased spatial resolution but requires careful consideration of how the density of electrodes affects the potentials being measured. Power differences as a function of electrode density and electrolyte spreading were examined and a method for correcting these differences was tested. METHODS: Separate EEG recordings from 8 participants were made using a high-density electrode net, first with 6 of 128 electrodes active followed by recordings with all electrodes active. For a subset of 4 participants measurements were counterbalanced with recordings made in the reversed order by drying the hair after the high-density recordings and using a fresh dry electrode net of the same size for the low-density recordings. Mean power values over 6 resting eyes open/closed EEG recordings at the 6 active electrodes common to both recording conditions were compared. Evidence for possible electrolyte spreading or bridging between electrodes was acquired by computing Hjorth electrical distances. Spherical spline interpolation was tested for correcting power values at electrodes affected by electrolyte spreading for these participants and for a subset of participants from a larger previous study. RESULTS: For both the complete set and the counterbalanced subset, significant decreases in power at the 6 common electrodes for the high-density recordings were observed across the range of the standard EEG bands (1-44 Hz). The number of bridges or amount of electrolyte spreading towards the reference electrode as evidenced by small Hjorth electrical distances served as a predictor of this power decrease. Spherical spline interpolation increased the power values at electrodes affected by electrolyte spreading and by a significant amount for the larger number of participants in the second group. CONCLUSIONS: Understanding signal effects caused by closely spaced electrodes, detecting electrolyte spreading and correcting its effects are important considerations for high-density EEG recordings. A combination of scalp maps of power density and plots of small Hjorth electrical distances can be used to identify electrodes affected by electrolyte spreading. Interpolation using spherical splines offers a method for correcting the potentials measured at these electrodes.

Adult↗
PubMed2006

Recording lead V(4)R is associated to enhanced use of fibrinolytic therapy in acute myocardial infarction.

BACKGROUND: ST-segment elevation in the right-sided chest lead V(4)R in inferior wall myocardial infarction is recognized as a sign of proximal occlusion of the right coronary artery with evolving right ventricular myocardial infarction. Our objective is to study how often lead V(4)R is recorded in clinical practice and how this might be associated with use of reperfusion therapy and outcome of patients. METHODS: Recording of lead V(4)R in 814 consecutive patients with acute myocardial infarction, administration of therapy, and outcome of the patients during a median follow-up of 285 days (174-313 days) were studied. RESULTS: V(4)R was recorded in 52% of patients with inferior ST-elevation myocardial infarction. Patients with V(4)R recorded were more likely to receive fibrinolytic therapy compared with patients without recording (65% vs 51%; P = .035). In multivariate analysis, recording of lead V(4)R (odds ratio [OR] 1.6, 95% confidence interval [CI] 1.1-2.2; P = .006), along with age (P < .001), previous myocardial infarction (OR 2.2, 95% CI 1.3-3.5; P = .002), and diabetes (OR 3.9, 95% CI 1.1-2.4; P = .03) correlated to the use of reperfusion therapy. Patients with lead V(4)R recorded had less (P = .055) reinfarction, unstable angina, stroke, and/or death during follow-up. CONCLUSIONS: Lead V(4)R was recorded in only half of patients with inferior ST-elevation myocardial infarction. Patients with V(4)R recorded were more likely to receive thrombolytic therapy than those without recording of the additional chest lead.

Aged↗
PubMed2005

Hardware-in-the-loop simulation and analysis of magnetic recording of nerve activity.

The focus of the reported research was on examination of properties of a special toroidal arrangement for magnetic recording of nerve activity. Toroidal high permeability coil placed around a nerve trunk can be used to record voltage induced by magnetic field generated by ionic nerve currents associated with propagating action potentials. The properties were examined in hardware-in-the-loop simulations that were used to identify the input-output relationship of the recording arrangement in case of different simulated intra-axonal current amplitudes and conduction velocities. Based on the recorded data, a nonlinear dynamical model (Wiener model) of the recording arrangement was identified, and subsequently used for predicting the voltage waveform expected in actual magnetic recording. This waveform was also used to estimate the potential of the method with the respect to obtainable signal quality (signal-to-noise (S/N) ratios). The manuscript also contains new theoretical results for sensitivity of toroidal and electroneurographic recording arrangements to different disturbances like, for example, EMG pickup. It can be concluded that high S/N ratios, short length, and superior disturbance rejection of the toroidal magnetic recording arrangement can make magnetic recording an attractive alternative to acute and chronic electroneurographic recording techniques.

Action Potentials↗
PubMed2006

Cell-attached voltage-clamp and current-clamp recording and stimulation techniques in brain slices.

Cell-attached recording provides a way to record the activity of - and to stimulate - neurons in brain slices without rupturing the cell membrane. This review uses theory and experimental data to address the proper application of this technique and the correct interpretation of the data. Voltage-clamp mode is best-suited for recording cell firing activity, and current-clamp mode is best-suited for recording resting membrane potential and synaptic potentials. The magnitude of the seal resistance determines what types of experiments can be accomplished with a cell-attached recording: a loose seal is adequate for recording action potential currents, and a tight seal is required for evoking action potentials in the attached cell and for recording resting and synaptic potentials. When recording action potential currents, if the researcher does not want to change the firing activity of the cell, then it is important that no current passes from the amplifier through the patch resistance. In order to accomplish this condition, the recording pipette should be held at the potential that gives a holding current of 0. An advantage of cell-attached current-clamp over whole-cell recording is that it accurately depicts whether a synaptic potential is hyperpolarizing or depolarizing without the risk of changing its polarity.

Action Potentials↗
PubMed1999

Simultaneous recording of mandibular condylar movement and single motor-unit activity at verified sites in the human lateral pterygoid muscle.

In recent years, understanding of normal jaw-muscle function has been enhanced by detailed descriptions of their complex internal architecture and of the functional activity of single motor units (SMUs). The lateral pterygoid muscle, however, has been poorly studied, although it is thought to play an important part in the control of jaw and jaw-joint movement. The present study is the first of a series of SMU studies to clarify the normal function of this muscle. The aims were to demonstrate (a) the unequivocal isolation of SMU activity from one or two verified recording sites within the lateral pterygoid, and (b) that these SMUs can be recorded reliably together with condylar movement during simple command jaw movements. Recordings of SMU activity were made with fine-wire electrodes from sites within the superior and inferior heads of the right lateral pterygoid during biting or command lateral jaw movements and combined with recordings of condylar and mid-incisor point movement. Recording sites were verified by computed tomography. In four young adults, the activities of 17 SMUs were reliably discriminated at seven recording sites within the lateral pterygoid. The units could be recorded during repeated trials of the same movement throughout a recording session with no appreciable change in amplitude or waveform. Units could also be discriminated simultaneously at separate recording sites--one in the superior head and the other in the inferior head. These data demonstrate that SMU activity can be recorded from verified sites within the lateral pterygoid simultaneously with condylar movement during command jaw movements.

Action Potentials↗
PubMed2000

The multifocal ERG in open angle glaucoma--a comparison of high and low contrast recordings in high- and low-tension open angle glaucoma.

High and low contrast multifocal ERG (MF-ERG) recordings were obtained from the right eyes of 24 patients with OAG (high-tension OAG: n=16, low-tension OAG: n=8) and compaired to those recorded from 18 healthy volunteers. High contrast MF-ERG recordings were obtained at a mean luminance of 100 cd/m2 with a contrast of 99%, while low contrast MF-ERGs were obtained at a mean luminance of 100 cd/m2 with a contrast of 50%. During MF-ERG recordings the central 50 degrees of the retina were stimulated by 103 hexagons. A MF-ERG recording lasted eight minutes, a M-sequence of 2(15) was used. The first order response component (KI, mean focal flash response) and the first and second slice of the second order response component (mean focal two flash interaction of flashes one, KII. 1, or two, KII.2, base intervals apart) were analyzed for group differences. Group differences were found mainly in latency measures. These included a delay in the central response average of the first positive peak, P1, in KII.2 (p < or = 0.05) in OAG high contrast recordings. Low contrast recordings showed a significant delay in the central response average of the first negative peak, Nl, in KII.2 as well as in the peripheral response average of N1 in KI and of P1 in KII.2 (p<0.05) in OAG. Amplitudes were only affected significantly in KI of the low contrast recordings. Here the amplitude N1P1 was significantly higher in high tension (n=16) than in low tension (n=8) OAG patients. However, an overlap in all of the response parameters tested allowed only group differences to be characterized. Under these stimulus conditions, neither high contrast recordings nor low contrast recordings seem sensitive enough to reliably recognize early glaucomatous retinal dysfunction.

Adolescent↗
PubMed1998

Recording of pacing stimulus artifacts by endovascular defibrillation lead systems: comparison of true and integrated bipolar circuits.

BACKGROUND: The occurrence ICD undersensing of ventricular fibrillation due to the presence of a pacing stimulus artifact (PSA) is in part related to the amplitude of the artifact recorded on the ICD rate sensing circuit. There is little comparative data regarding PSA amplitude recorded by commercial ICD rate-sensing circuits. PURPOSE: To compare PSA amplitude recorded by commercial endovascular defibrillation leads utilizing integrated or true bipolar sensing circuits. METHODS: Nineteen large (60-120 kg) pigs were utilized. Two different commercial endovascular defibrillation leads were evaluated, each with its distal tip located at the right ventricular apex: (1) Medtronic Transvene; and (2) CPI Endotak. Three different rate-sensing circuits were evaluated: (1) Transvene true bipolar (tip-ring); (2) Transvene integrated bipolar (tip-coil); and (3) Endotak integrated bipolar (tip-coil). Using a separate pacing lead located at the left ventricular apex (n = 19 animals) or right ventricular outflow tract (n = 10 animals), pacing was performed at a pulse width of 0.5 milliseconds at outputs of 1.5, 5 and 10 volts. PSA amplitude was recorded at each output by each circuit. RESULTS: During pacing from the left ventricular apex, at each pacing output voltage the PSA amplitude recorded by the true bipolar circuit (0.6 +/- 0.1 mV at 1.5 volts, 2.0 +/- 0.5 mV at 5 volts, 3.7 +/- 0.8 mV at 10 volts) was significantly smaller than recorded by the Transvene integrated circuit (1.4 +/- 0.3 mV at 1.5 volts, 3.8 +/- 0.7 mV at 5 volts, 4.1 +/- 0.8 mV at 10 volts) or the Endotak integrated circuit (1.8 +/- 0.4 mV at 1.5 volts, 4.2 +/- 1.0 mV at 5 volts, 6.3 +/- 1.8 mV at 10 volts). During pacing from the right ventricular outflow tract, at each pacing output voltage the PSA amplitude recorded by the true bipolar circuit (0.7 +/- 0.1 mV at 1.5 volts, 1.7 +/- 0.4 mV at 5 volts, 4.0 +/- 0.7 mV at 10 volts) was significantly smaller than recorded by the Transvene integrated circuit (1.1 +/- 0.4 mV at 1.5 volts, 3.9 +/- 1.2 mV at 5 volts, 7.5 +/- 1.8 mV at 10 volts) or the Endotak integrated circuit (1.6 +/- 0.7 mV at 1.5 volts, 4.3 +/- 1.7 mV at 5 volts, 7.5 +/- 2.6 mV at 10 volts). For both pacing sites, the PSA amplitude recorded by the two integrated circuits was not significantly different. CONCLUSIONS: For a given pacing output voltage, PSA amplitude recorded by commercial endovascular rate sensing/defibrillation leads is greater when the sensing circuit is integrated than when it is true bipolar. These data may be helpful in planning ICD implantation in patients with previously implanted permanent pacemakers.

Animals↗
PubMed1998

Biliary, pancreatic, and sphincter of Oddi electrical and mechanical signals recorded during ERCP.

Measurements of biliary tract motility have focused on radiologic and pressure measurements to quantify biliary motility rather than measurements of electrical activity of the biliary tract. We previously reported the recording of biliary electrical signals during ERCP and now report on the continued development and validation of a system to measure biliary tract electrical activity as well as biliary mechanical activity. In 26 patients presenting with a variety of clinical indications, we recorded measurements of electrical activity from the common bile duct sphincter (16 patients), pancreatic duct sphincter (eight patients), and/or sphincter of Oddi (eight patients). Electrical recordings were performed with a specially modified ERCP catheter, using two circular electrodes as well as a custom catheter that measured both electrical and mechanical activity. Electrical activity of the biliary tract was successfully recorded in 25 of 26 patients (96%), including the common bile duct sphincter (16 patients, 62%), pancreatic duct sphincter (eight patients, 31%) and sphincter of Oddi (eight patients, 31%). Along with the electrical recordings, common bile duct sphincter mechanical activity was recorded in 12 patients (67%), pancreatic duct sphincter mechanical activity in six patients (33%), and sphincter of Oddi mechanical activity in six patients (33%). Frequency analysis of electrical signals revealed a mean frequency (cycles/min) of 4.7 +/- 0.5 in the common bile duct sphincter, 4.1 +/- 0.6 in the pancreatic duct sphincter, and 4.9 +/- 0.7 in the sphincter of Oddi. Phasic mechanical frequency in cycles per minute was recorded at a frequency of 4.8 +/- 0.5 in common bile duct sphincter, 4.0 +/- 0.6 in pancreatic duct sphincter, and 5.3 +/- 0.9 in sphincter of Oddi. Tonic pressure (averaged 12.1 +/- 1.5 mm Hg) in common bile duct sphincter, 12.4 +/- 1.4 mm Hg in pancreatic duct sphincter, and 15.0 +/- 5.1 mm Hg in sphincter of Oddi. Analysis of wave form propagations (noted as percentage antegrade, retrograde, or indeterminant) revealed 50% antegrade, 23% retrograde, and 27% indeterminant). One patient was recorded on two occasions via ERCP; the same patient had an intraoperative recording. All three recordings showed similarities. We conclude that measurements of biliary, pancreatic, and sphincter of Oddi electrical and mechanical activity are feasible and can be done as part of ERCP. There was good correlation between biliary tract electrical and mechanical events and different wave form characteristics were noted for different parts of the biliary tree. Further studies are warranted to evaluate the potential usefulness of measurement of biliary tract electrical activity, and to confirm its correlation with mechanical events in the pancreato-biliary tree.

Adult↗
PubMed2006

Evaluation of external radiation dosimetry records at the Savannah River Site, 1951-1989.

The Savannah River Site (SRS) is one of the largest facilities in the nation's nuclear weapons complex. To date, little information has been published regarding radiation risk estimates derived from epidemiological studies of SRS workers. As part of an ongoing epidemiological cohort study of SRS workers, we have assessed the suitability of the Site's personnel radiation dosimetry information for use in epidemiological analyses. This paper provides information on historical dosimetry methods, recording practices, and the completeness of computerized dosimetry information for workers employed at SRS during the period 1951-1989, when the site was operated by the du Pont Company. The study includes 18,883 workers hired at SRS between 1951 and 1987 who were employed for at least 90 days. Documents relating to external radiation dosimetry methods were reviewed, recorded doses were examined to evaluate recording practices, and the completeness of monitoring was assessed by comparing employment history and computerized dosimetry records, and by implementing a "nearby" procedure for estimating values for missing annual dosimetry records. Dosimeter technology evolved over this period from two-element film dosimeters to multielement thermoluminescent dosimeters. Dosimetry measurements were recorded consistently in 0.05 millisievert (mSv) increments. Prior to 1973, recording thresholds of 0.10-0.15 mSv were used while from 1973 to 1989 a recording threshold of 0.05 mSv was used. We abstracted nearly 3 person-Sv of dosimetry information that was available in hardcopy but not in computerized format. The collective dose from the computerized and abstracted records totaled 512.1 person-Sv. A "nearby" method was used to estimate dose values for 13,812 employment-years for which dosimetry information was not available. The average estimated value was 0.6 mSv and the assigned collective dose derived via the "nearby" procedure was 8.7 person-Sv. The consistency of dosimetry practices at SRS and the completeness of historical dosimetry records are supportive of their use in epidemiologic research.

Georgia↗
PubMed2003

Diagnostic yield of external electrocardiographic loop recorders in patients with recurrent syncope and negative tilt table test.

External electrocardiographic loop recording permits extended cardiac rhythm monitoring and ECG storage before and after device activation. The purpose of the study was to assess the diagnostic yield of external loop recorders in patients with more than two syncopal events within the last 6 months and a negative tilt table test. Twenty-four consecutive patients (51 +/- 14 years, male n = 9) were enrolled with 3 +/- 4 recurrent syncopal events within the last 6 months and no overt structural heart disease. The loop recorder CardioCall continuously records a two-channel ECG via skin electrodes. When activated, up to 4.5 minutes of the ECG preceding activation is stored. The time between tilt table testing and monitoring was 5 +/- 4 weeks. The average monitoring period covered 50 +/- 22 days. Recording was either unsuccessful or terminated prematurely in 5 patients. The reasons were skin irritation secondary to the electrodes in two patients, cable damage in one patient, and two patients inadvertently erased the stored data when replacing the batteries. Fourteen patients activated the loop recorder at least once. Symptoms leading to device activation were syncope (n = 1), dizziness (n = 11), feeling unwell (n = 7), palpitations (n = 5), headaches (n = 1), and chest pain (n = 1). The loop recorder documented sinus tachycardia during the syncopal event. Sinus tachycardia was also observed in 7 other patients, and atrial flutter in two patients. Eight patients had recurrent syncope with two patients experiencing syncope prior to the monitoring period, one syncope occurred in a patient who inadvertently erased the stored data, one event coincided with sinus tachycardia, and 4 (17%) patients had syncope during 15 +/- 10 months after termination of loop monitoring. The external loop recorder was not very useful for arrhythmia detection in patients with syncopal events, no overt heart disease, and a negative tilt table test because the cardiac rhythm was stored in only 1 of 8 (13%) patients with recurrent syncope. Reasons for the low diagnostic yield of external loop recorders were infrequent syncopal events after the baseline evaluation, with rare events during the limited monitoring period in particular, and premature termination or unsuccessful recording in 21% of patients.

Arrhythmias, Cardiac↗
PubMedDate not supplied

[The importance of the common cancer registry for the identification of cancer cases in the EPIC Potsdam-study -- results of the first record linkage].

AIM: The follow-up of the European Prospective Investigation into Cancer and Nutrition (EPIC)-Potsdam study has been identifying cancer diagnoses by an active follow-up through participant's self-report which is then confirmed by pathology registries or medical doctors. To utilise another source of information, a record linkage was performed with the Common Cancer Registry (CCR) of the states of Berlin, Brandenburg, Mecklenburg-Western Pomerania, Saxony-Anhalt and of the free states Saxony and Thuringia in November 2001, using the EPIC-Potsdam database of compliant study participants at that point in time (n = 27 087). This methodological study compares data of identified cancer cases in the EPIC-Potsdam study with those generated through the record linkage. METHODS: The GKR identified 1468 study participants of the EPIC-Potsdam study. Cases (n = 108) with non-melanoma skin cancer were excluded. A separate analysis was done for prevalent (date of cancer diagnosis before baseline examination) and incident cancers (date of diagnosis after baseline examination). We examined how many subjects with at least one cancer were known to EPIC-Potsdam and the CCR, how many had been known only to the CCR and how many only to the EPIC-Potsdam study. Of incident cancer cases each diagnosis was counted. It was analyzed whether the diagnoses as they had been collected by EPIC-Potsdam were identified by the record linkage. Focus was on the diagnoses that had been unknown in EPIC-Potsdam before. The concordance of information from both sources was also considered. RESULTS: According to the record linkage, 1298 subjects with at least one prevalent cancer were identified in the EPIC-Potsdam cohort, 593 (46 %) of whom were identified in both data sources, 241 (19 %) were newly identified, and 464 (36 %) participants self-reported at least one prevalent tumour which was not identified through the record linkage. Seven tumours were diagnosed before 1961 (the CCR's computerised data are only available since 1961). Fifty-seven percent (n = 187) of all tumours which could not be identified in the cancer registry dated from 1990 - 1995. After completion of the record linkage a total of 582 medically verified incident cancer cases were identified. These comprised 397 medically verified cases that were identified in the EPIC-cohort study prior to the record linkage, 18 self-reported cases where the medical verification was pending, and 167 newly identified cases. Eighty-five of the latter cases have not been identified by other sources in the two following years after record linkage indicating that 15 % of the medically verified cases have been found solely through the linkage. CONCLUSION: The EPIC-Potsdam study had a significant benefit of the record linkage due to both the additional identification and verification of prevalent and incident cancer cases, as well as a timely advanced identification of incident diagnoses. The record linkage with the cancer registry improved the quality of the endpoint data of the EPIC-Potsdam study.

Adult↗
PubMed1986

Origin of short-latency somatosensory evoked potentials to median nerve stimulation in the cat. Comparison of the recording montages and effect of laminectomy.

Short-latency somatosensory evoked potentials were recorded from 23 cats with the frontal-neck, scalp-ear and scalp-noncephalic reference montages. In the frontal-neck recordings, four or five components (n9, n11, n13a, n13b and n14) were identified, whereas three components (p15, p18 and p20) were recorded in the scalp-ear leads. The noncephalic reference recordings had four to six components (p9, p10, p11, p13a, p13b and p14). The origin of these components was investigated by recording direct from the attributed generators and examining the effects of lesions. The suggested generators are as follows: n9, p9 and p10-peripheral nerve; n11, p11-dorsal column; n13a-segmental dorsal horn; p13a-spinocerebellar tract; n13b and p13b-cuneate nucleus and caudal part of the medial lemniscus; n14, p14 and p15-rostral part of the medial lemniscus; p18-thalamocortical radiation; p20-primary somatosensory cortex. Components with similar latencies such as n13a and p13a in the frontal-neck and noncephalic reference recordings had different generators. In the noncephalic reference recordings, the axially orientated dipoles, including the potential produced by the spinocerebellar tract (p13a) were clearly detectable, but the transversely orientated dipole of the segmental dorsal horn (n13a) was indistinct. The frontal-neck montage was distorted by the frontal 'reference' electrode active for part of the axially ascending volleys (p13a in some cats and p14), but could pick up the near-field potentials in the segmental dorsal horn (n13a). Desynchronized volleys in fibre tracts such as the spinothalamic tract did not contribute significantly to the potentials recorded from the skin, whereas the synaptic potential in the cuneate nucleus was shown to have a steep onset and open-field distribution with its dipole orientated in part axially, and was recorded in the noncephalic reference montage. The p9 and p11 positivities fused after laminectomy, suggesting that conductance change at the root entry to the bony spinal canal separates these components in the noncephalic reference recording.

Anesthesia↗
PubMed1996

Comparison of dose histories for U.S. nuclear power plant workers, based on records held by a major dosimetry service company and on the NRC REIRS database.

In order to conduct valid epidemiological studies of nuclear power plant workers, good information on the workers' radiation dose histories is essential. Dose records held by a major dosimetry service company and on the Nuclear Regulatory Commission's Radiation Exposure Information and Recording System have been compared for a sample of 99 workers. About half of the workers in the sample had no records on the Radiation Exposure Information and Recording System, since they had not terminated employment at a Nuclear Regulatory Commission-licensed facility; accordingly, their career doses (as recorded by the service company) were generally higher than those for workers on the Radiation Exposure Information and Recording System. For nearly half of the workers with records on both databases, the total dose recorded for terminated employments at nuclear power plants differed by at least a factor of 5 between the databases. In absolute terms, these differences were of the order of 100 mSv or more. An approach that utilized both the Radiation Exposure Information and Recording System and the dosimetry service company's records might be of value in constructing dose histories for a large epidemiological study. However, the comparisons presented here support the initiatives of the Nuclear Regulatory Commission to request licensees to report voluntarily career doses for current employees. These data are essential if a large and valid epidemiological study of nuclear plant workers is to be conducted in the foreseeable future.

Humans↗
PubMed1998

Axillary somatosensory evoked potential response: an alternate peripheral recording site.

When recording upper-extremity somatosensory evoked potentials (SSEP), the standard peripheral recording site is Erb's point located near the clavicle. During some surgical procedures, the Erb's point recording site is often either part of the surgical field or is distorted by patient size or trauma. In the present study, we evaluated the usefulness of the axillary fossa as an alternate peripheral recording site. Using standard recording techniques, we studied 29 patients (54 limbs); studied: 19 as outpatients and 10 during surgery. Evoked responses subsequent to median nerve stimulation were recorded with the following montage: Axi-Axc, Epi-Epc, C5S-Cz or Fz, and Cpi-Cpc. The potential recorded at the axillary site, termed axillary response (Ax), produced a waveform similar in morphology to that of the Erb's point response and displayed a generally well defined, prominent negative peak occurring approximately 2.5 ms earlier than that of Erb's point. We conclude that the axillary space in the lateral part of the upper chest and medial side of the arm is an appropriate alternate site for recording peripheral potentials after stimulation of the median nerve. The Ax recording site is useful during surgery when the Erb's point site is unavailable. Further study of this recording site is necessary to determine its diagnostic usefulness.

Adult↗