Biomedical subjects

S Hollerbach

Publications and source records attributed to S Hollerbach.

At least 37 records · Page 2Linked to original sources

PubMed2001

Endoscopic ultrasonography (EUS) and fine-needle aspiration (FNA) cytology for diagnosis of chronic pancreatitis.

BACKGROUND AND STUDY AIMS: Previous studies have shown that endoscopic ultrasonography (EUS) sensitively detects morphologic abnormalities due to chronic pancreatitis. However, morphologic EUS findings have limited specificity, particularly at the early stages of chronic pancreatitis. Our aims were to study pancreatic morphology and inflammation in patients with chronic pancreatitis, using EUS and fine-needle aspiration cytology (EUS-FNA), and to compare the results with those of endoscopic retrograde cholangiopancreatography (ERCP) and pancreatic function tests. PATIENTS AND METHODS: 37 patients (48 +/- 13 years) with clinical symptoms and laboratory test findings suggestive of chronic pancreatitis were prospectively studied. Patients with malignancy or major concomitant disorders were excluded. Clinical evaluation included indirect pancreatic function tests. Morphologic criteria for chronic pancreatitis included echo-intense septae/echo-reduced foci (i. e. pseudolobularity), ductal irregularities, and calcifications. EUS-FNA was performed in 27/37 patients, by means of the Hitachi FG34-UX echo endoscope and a 22-gauge needle, and tissue specimens were submitted for standard cytological evaluation. ERCP served as reference in all patients, using the Cambridge classification. RESULTS: 31 patients had chronic pancreatitis while six had normal findings at ERCP. EUS showed morphologic abnormalities of the pancreas in 33 patients. Morphologic abnormalities alone reached a sensitivity of 97 % for chronic pancreatitis with a specificity of only 60 %, while the positive predictive value (PPV) was 94 %, and the negative predictive value (NPV) was 75 %. EUS-FNA increased the negative predictive value to 100 % and the specificity to 67 %. On average, 2.3 needle passes were necessary to obtain sufficient amounts of tissue. The correlation of EUS findings with pancreatic function tests was poor. EUS results were in agreement with regard to the severity of chronic pancreatitis in 5/8 patients with grade I disease, in 11/13 patients with grade II, and in 10/10 patients with grade III disease. Minor complications occurred in two patients (7 %). CONCLUSIONS: EUS is as sensitive and effective as ERCP in the detection of chronic pancreatitis, particularly when only mild disease is present. However, EUS findings have limited specificity, particularly in patients with mild disease. EUS-FNA with cytology is safe and improves the negative predictive value. Negative EUS-FNA findings rule out chronic pancreatitis, but cytological investigation alone does not improve the specificity of EUS findings, suggesting that further improvements in tissue sampling and analysis are necessary to support routine use of FNA in patients with chronic pancreatitis.

Adult↗

PubMed2001

Brain electrical activity mapping of EEG for the diagnosis of (sub)clinical hepatic encephalopathy in chronic liver disease.

We studied the role of brain electrical activity mapping (BEAM) in the assessment of neuropsychiatric disturbances in 48 cirrhotic patients without clinical evidence of hepatic encephalopathy (no HE, n = 19), with subclinical HE (grade 0, denoting pathological psychometric tests, n = 13) and mild-to-moderate HE (grade I, n = 6; grade II, n = 10). Results were compared with 23 healthy controls. BEAM variables quantified were: (i) the peak frequency (PF); (ii) the amplitude of PF; and (iii) the topographic localization of the maximum peak amplitude digitized for quantification by using a coordinate system. Mean amplitudes and their topographic localization in the following frequency-bands were analysed: delta (1.0-3.5 Hz), theta (4.0-7.5 Hz), alpha 1 (8.0-9.5 Hz), alpha 2 (10.0-11.5 Hz), beta 1 (12.0-15.5 Hz), beta 2 (16.0-19.5 Hz), and beta 3 (20.0-23.5 Hz). The PF was significantly slower in all HE patients than in healthy controls (8.5 +/- 2.0 Hz v. 10.1 +/- 1.0 Hz, P< 0.001). Even in no HE, the PF was significantly slower than in controls (8.6 +/- 1.5 Hz v. 10.1 +/- 1.0 Hz, P< 0.01). No relevant topographic differences of PF were observed. The mean amplitudes of the following bands differed significantly between controls and patients: theta (increased in HE, P< 0.05), alpha 2 (decreased in HE, P< 0.05), and beta 2 and beta 3 (increased in HE, (P < 0.05). In HE patients, the topographic localization of all beta bands showed a significant shift from parieto-occipital areas to central areas of the cortex. We conclude that BEAM is a sensitive tool for detecting neuropsychiatric disturbances in cirrhotics with no HE and with subclinical HE. The combination of PF in the theta band, increased mean amplitude in the beta 2 band, and the localization of the latter band in the frontocentral area of the cortex is an objective and sensitive tool for identifying neuropsychiatric disturbances in 85% of cirrhotic patients with no HE. Further studies are required to determine the clinical implications of these abnormal findings in the absence of overt clinical symptoms.

Adult↗

PubMed2001

Cardiac autonomic function and oesophageal acid sensitivity in patients with non-cardiac chest pain.

BACKGROUND: Acid reflux can elicit non-cardiac chest pain (NCCP), possibly through altered visceral sensory or autonomic function. The interactions between symptoms, autonomic function, and acid exposure are poorly understood. AIM: To examine autonomic function in NCCP patients during exposure to oesophageal acid infusion. SUBJECTS AND METHODS: Autonomic activity was assessed using power spectral analysis of heart rate variability (PSHRV), before and during oesophageal acidification (0.1 N HCl), in 28 NCCP patients (40.5 (10) years; 13 females) and in 10 matched healthy controls. Measured PSHRV indices included high frequency (HF) (0.15-0.5 Hz) and low frequency (LF) (0.06-0.15 Hz) power to assess vagal and sympathetic activity, respectively. RESULTS: A total of 19/28 patients had angina-like symptoms elicited by acid. There were no significant manometric changes observed in either acid sensitive or insensitive patients. Acid sensitive patients had a higher baseline heart rate (82.9 (3.1) v 66.7 (3.5) beats/min; p<0.005) and lower baseline vagal activity (HF normalised area: 31.1 (1.9)% v 38.9 (2.3)%; p< 0.03) than acid insensitive patients. During acid infusion, vagal cardiac outflow increased (p<0.03) in acid sensitive but not in acid insensitive patients. CONCLUSIONS: Patients with angina-like pain during acid infusion have decreased resting vagal activity. The symptoms elicited by perception of acid are further associated with a simultaneous increase in vagal activity in keeping with a vagally mediated pseudoaffective response.

Adult↗

PubMed2000

Abnormal cerebral processing of oesophageal stimuli in patients with noncardiac chest pain (NCCP).

In noncardiac chest pain (NCCP), altered visceral perception may result from abnormal cerebral processing of sensory input rather than abnormalities of afferent pathways. However, the interactions between symptoms, autonomic function and oesophageal stimuli are poorly studied. Oesophageal stimulation elicits reproducible cortical evoked potentials [CEP] and modulates heart rate variability via vagal pathways, as visible on power spectrum analysis of heart rate variability [PS-HRV]. These methods are increasingly used to study the function of visceral afferent neural pathways in human. The aim of this study was to compare EP and PS-HRV during oesophageal stimuli in NCCP and controls. Twelve healthy volunteers (one female, 11 male; aged 24-51 years; mean 32 +/- 8 years), and eight NCCP patients (three female, five male; age range 26-58, mean 40.5 +/- 10 years) were studied. Electrical oesophageal stimulation (EOS; 200 microseconds, 0.2 Hz, 25 stimuli) was applied to the oesophageal wall 5 cm above the lower oesophageal sphincter (LOS), and perception thresholds (measured in mA) determined. EP responses were recorded using 22 standard electroencephalogram scalp electrodes. Autonomic activity was assessed using PS-HRV, before, during, and after oesophageal stimulation. Measured PS-HRV indices included high frequency (HF; 0. 15-0.5 Hz) and low frequency (LF; 0.06-0.15 Hz) power, respectively, assessing vagal and sympathetic activity, and the LF/HF ratio. EOS perception occurred at lower thresholds in NCCP than in controls (3. 6 +/- 1 vs. 7.8 +/- 2 mA, P < 0.05). EP amplitude was greater (13 +/- 2 vs. 6 +/- 1 microV, P < 0.0001), and latency longer in controls vs. NCCP (191 +/- 7 ms vs. 219 +/- 6 ms, P < 0.001). In NCCP, EOS decreased sympathetic outflow (low frequency peak on PS-HRV) and increased cardiovagal activity (high frequency peak, P < 0.02) to a significantly higher degree in comparison with controls. During EOS, heart rate decreased in NCCP from 68 vs. 62 beats min-1 (P < 0.003) but not in controls. In NCCP patients, EOS was perceived at lower intensities and was associated with a greater cardiovagal reflex response. EP responses associated with EOS were smaller in NCCP than in controls, suggesting that an increased perception of oesophageal stimuli results from an enhanced cerebral processing of visceral sensory input in NCCP, rather than from hyperalgesic responses in visceral afferent pathways.

Adult↗

PubMed2000

[Pulmonary metastasis of extranodal high malignancy B-cell non-Hodgkin lymphoma of the bulbus duodeni and pylorus of the stomach].

We report a 71-year-old female patient with repeated vomitus, meteorism, epigastric pain and reflux for more than four month. She had a palpable mass in the upper abdomen and lost 7 kg of weight during the last four months. Chest X-ray showed two masses, 2 cm and 3 cm in diameter, in the left and right lower lung. A stenosing polypoid mucosal swelling in the antrum and the duodenal bulb. The pulmonal masses were biopsied under CT-guidance. Biopsy proved a high malignant B-cell non-Hodgkin's lymphoma of the stomach. The masses in the lung were identified as metastases of the gastrointestinal lymphoma. In conclusion on this tumor was an extranodal non-Hodgkin's lymphoma stadium BE IV according to Musshoff. A CHOP-chemotherapy was initiated. Restaging after three cycles of CHOP revealed a complete remission. Primary gastrointestinal non-Hodgkin's lymphomas are relatively rare neoplasms of the abdomen. Unusual and interesting in this case ist the metastatic pattern involving the lung periphery without local lymph node metastases.

Aged↗

PubMed2000

Effects of esophageal stimulation in healthy subjects.

We studied the effects of esophageal electrical stimulation on heart rate variability power spectra (PS/HRV) and cortical evoked potentials (EPs) in healthy subjects. The intensity of stimulation was varied from 2.7 to 20 mA. We found that the amplitude of the cortical evoked potentials (amplitude of the N2/P2 peak) increased from 5.1 +/- 0.7 microV at 5 mA to 16.3 +/- 1.1 microV at 20 mA. The PS/HRV showed an increase in the vagal modulation of the sinus node. When the stimulation frequency was varied from 0.1 to 1 Hz at a constant intensity of 15 mA, the amplitude of cortical EPs (N2/P2 peak) decreased with increase in the frequency of stimulation (p < 0.05). The LF:HF ratio decreased significantly for all frequencies of stimulation (p < 0.005). An experimental paradigm to evoke the cognitive component in the cortical EPs yielded a peak around 354 ms following the stimulus.

Cerebral Cortex↗

PubMed2000

Effects of esophageal stimulation in patients with functional disorders of the gastrointestinal tract.

We studied the effects of esophageal electrical stimulation on cortical-evoked potentials (EPs) and power spectrum of heart rate variability (PS/HRV) in patients with diabetes and non-cardiac chest pain (NCCP). We also recorded cognitive-evoked potentials (P300 EPs) in response to an odd-ball stimulation in patients with NCCP. Diabetic patients did not yield reproducible cortical EPs. Their power spectra of heart rate variability (PS/HRV) showed an increased vagal modulation during stimulation. In patients with NCCP the P300 EPs were of greater amplitude (17 +/- 3 microV vs. 12 +/- 1 microV in controls, p < 0.04), while peak latencies were slightly elongated in patients (382 +/- 22 ms vs. 354 +/- 12 ms in controls). The PS/HRV in these patients also showed an increased vagal modulation of the sinus node activity. Our results suggest the following: (1) in patients with diabetes, afferent pathways and processing of sensory signals are likely to be impaired; (2) an increased perception of esophageal stimulation reflects an exaggerated brainstem response and altered cortical processing of visceral sensation in patients with NCCP.

Adolescent↗

PubMed1999

Cognitive evoked potentials to anticipated oesophageal stimulus in humans: quantitative assessment of the cognitive aspects of visceral perception.

Evoked potential studies provide an objective measure of the neural pathways involved with perception. The effects of cognitive factors, such as anticipation or awareness, on evoked potentials are not known. The aim was to compare the evoked potential response to oesophageal stimulation with the cortical activity associated with anticipation of the same stimulus. In 12 healthy men (23.5 +/- 4 years), oesophageal electrical stimulation (15 mA, 0.2 Hz, 0.2 msec) was applied, and the evoked potentials recorded using scalp electrodes. A computerized model of randomly skipped stimuli (4:1 ratio) was used to separately record the evoked potentials associated with stimulation and those associated with an anticipated stimulus. The electrical stimulus represented the nontarget stimulus and the skipped impulse the target (anticipatory) stimulus. This anticipatory evoked potential was also compared to auditory P300 evoked potentials. Reproducible evoked potentials and auditory P300 responses were elicited in all subjects. Anticipatory evoked potentials (peak latency 282.1 +/- 7.9 msec, amplitude 8.2 +/- 0.7 microV, P < 0.05 vs auditory P300 evoked potential) were obtained with the skipped stimulus. This anticipatory evoked potential was located frontocentrally, while the auditory P300 potential was located in the centro-parietal cortex. The anticipatory evoked potential associated with expectation of an oesophageal stimulus, although of similar latency to that of the auditory P300 evoked response, originates from a different cortical location. The recording of cognitive evoked potentials to an expected oesophageal stimulus depends on attention to, and awareness of, the actual stimulus. Anticipatory evoked potentials to GI stimuli may provide an objective electrophysiological tool for the assessment of the cognitive factors associated with visceral perception.

Adult↗

PubMed1998

Neurocardiac and cerebral responses evoked by esophageal vago-afferent stimulation in humans: effect of varying intensities.

OBJECTIVE: This study was designed to determine whether esophageal vago-afferent electrostimulation, over a wide range of stimulus intensities, can sustain a cardiac vago-efferent effect by way of central nervous system processing. METHODS: Studies were performed in ten healthy male subjects (23.9 +/- 6.3 years). Esophageal electrostimulation was carried out using a stimulating electrode placed in the distal esophagus. Stimulation of esophageal vago-afferent fibres was employed using electrical impulses (200 microseconds at 0.2 Hz x 128 s) varying from 2.7 to 20 mA. Respiratory frequencies, beat-to-beat heart rate autospectra and cerebral evoked potentials were recorded at baseline and at each stimulus intensity in random order. RESULTS: With esophageal electrical stimulation, we observed a small non-significant decrease in heart rate. There was a dramatic shift of the instantaneous heart rate power spectra towards enhanced cardiac vagal modulation with intensities as low as 5 mA. This effect was sustained throughout all intensities with no further change in either the low frequency or high frequency power. Conversely, there was a linear dose response relationship between cerebral evoked potential amplitude and stimulus intensity mainly occurring above perception threshold (10 mA). Esophageal stimulation had no significant effect on heart rate or respiratory frequency at any stimulus intensity. CONCLUSIONS: These results indicate that electrical stimulation of the distal esophagus across a wide range of current intensities elicits a reproducible shift in the heart rate power spectrum towards enhanced vagal modulation. The data suggest a closed loop afferent/efferent circuitry wherein tonic visceral afferent impulses appear to elicit a phasic or modulatory vago-efferent cardiac response in healthy subjects.

Adult↗

PubMed1998

Cortical evoked responses following esophageal balloon distension and electrical stimulation in healthy volunteers.

Recording of evoked potential responses represents an objective and quantifiable method to study visceral afferent sensory pathways in humans. We examined the evoked responses to mechanical distension (balloon) and electrical stimulation of the proximal and distal esophagus. A standard manometric catheter with a latex balloon and an additional electrode attached to its body was placed in the lower esophagus in 15 healthy young volunteers. Repeated nonpainful balloon distension stimuli above the individual sensation threshold (0.17 Hz, 12-20 ml) or short electrical impulses (0.2 Hz, 12-16 mA) were delivered in an alternate fashion at 23 and 33 cm from the nares. Evoked potential responses (EP) were recorded through 22 scalp surface electrodes using the standard 10/20 International EEG system of electrode placement. Balloon distension produced a reproducible triphasic response at both sites. Peak latencies of three negative EP peaks were 92+/-17, 229+/-40, and 339+/-36 msec with proximal stimulation versus 154+/-24, 275+/-24, and 384+/-30 msec obtained with distal stimulation (P < 0.001). Electrical stimulation produced a triphasic response with significantly shorter peak latencies at both sites when compared to mechanical stimulation (P < 0.001). Peak latencies were 74+/-12, 137+/-11, and 245+/-27 msec proximal versus 83+/-12, 148+/-32, and 247+/-51 msec with distal stimulation (P < 0.01). The calculated conduction velocities for both modes of stimulation (balloon: 1.73+/-0.9 m/sec vs electrical: 10.1+/-3.4 m/sec) are compatible with conduction through C fibers and Adelta fibers, respectively. Both modes of stimulation produce characteristic brain responses that are conveyed through different types of afferent fibers. The respective contributions of both types of fibers to esophageal function and symptomatology can be specifically addressed using this approach in both normal and pathologic conditions.

Adult↗

PubMed1998

The accuracy of abdominal ultrasound in the assessment of bowel disorders.

BACKGROUND: Little is known about the sensitivity, specificity, and predictive values of transabdominal ultrasonographic (US) findings in a teaching hospital setting. METHODS: We carried out a prospective study including 227 patients with symptoms suggestive of inflammatory bowel disorder. The Picker 9200 CS equipment (5-mHz curved-array probe) was used to obtain bowel images. Gastrointestinal endoscopy, enteroclysis, bowel enema, computed tomography scan, or bowel surgery was used as reference. RESULTS: Of 227 patients, 168 had pathologic findings of the bowel as final diagnosis. The overall sensitivity of US was 76%, whereas the positive predictive value was 98%. Overall specificity was 95%. The negative predictive value for bowel disorders was only 58%, since US missed pathologic findings in 48 patients. Subgroup analysis showed a sensitivity of 84% for Crohn's disease, 66% for ulcerative colitis, 46% for bowel tumors, and 60% for diverticulitis. Topographic comparisons showed that US detected inflammatory bowel-wall alterations preferentially in the terminal ileum and colon, whereas abnormalities in the duodenum, jejunum, and rectum were frequently missed (sensitivity, 10%-20%). CONCLUSIONS: Positive US findings are useful for the diagnosis of bowel processes. US is highly predictive albeit not disease-specific. Negative US examinations, however, do not exclude pathologic bowel processes. A topographic location of pathologic US findings is mostly confined to the colon.

Adult↗

PubMed1998

Assessment of afferent gut--brain function using cerebral evoked responses to esophageal stimulation.

Increasing awareness is attributed to altered sensory perception in the pathogenesis of gastrointestinal disorders. Evoked potentials (EP), which represent the brain's electrical response to peripheral stimulation, have recently been used to investigate where and how (GI) afferent information is processed along the brain-gut axis. EP can be obtained with electrical stimulation or balloon distention in the esophagus in humans. Stimulation of afferent neural pathways in the esophagus produces cerebral evoked responses allowing assessment of the peripheral afferent neural pathways involved, and of the function of integrative neural centers within the brain. Recent studies using esophageal EP indicate that the cerebral response to either mode of stimulation depends on the perception of the stimuli. Using electrical stimulation, a clear dose-response relationship is found. The EP response obtained with electrical stimulation is in keeping with those recorded using direct cervical stimulation of the vagus nerve, supporting evidence that esophageal EP are produced by activation of afferent vagal pathways. From the conduction velocity of the autonomic (vagal) nerves conveying information from esophagus to brain, it was concluded that non-painful electrical stimuli predominantly activate fast conducting myelinated afferent sensory fibers (A-fibers), while EP to balloon distention are largely due to activation of unmyelinated C-fibers. Techniques, however, vary widely amongst different investigators, and some electrophysiological parameters remain controversial, as there is no standard approach. Using balloon distention, EP waveforms vary widely between laboratories, suggesting that EP are substantially influenced by the stimulator devices (pump, respirator). EP to balloon distention are hampered by a relatively low signal-to-noise ratio (SNR), which is probably due to long inflation-deflation time (> 200 ms). With electrical stimulation, there is much less variability between different groups, and SNR is distinctly higher. This method appears to be most attractive for studies of afferent esophageal function. Standardization of the techniques is important, before esophageal EP can be regarded as a useful diagnostic approach in patient groups.

Afferent Pathways↗

PubMed1997

Estimation of habituation and signal-to-noise ratio of cortical evoked potentials to oesophageal electrical and mechanical stimulation.

Electrical and mechanical stimulation of the oesophagus has been recently proposed to examine the physiological effects of autonomic stimulation in humans. Cortical evoked potentials (EPs) to oesophageal stimulation provide an assessment of afferent fibres and central processing. However, habituation takes place during averaging of cortical EPs and reduces the signal-to-noise ratio (SNR) as the number of stimuli increases. The SNR of cortical EPs to oesophageal stimulation is computed for 15 normal subjects. Habituation is characterised by the Euclidean distance between the EEG response to single stimuli and the averaged EP, to serve as an objective measure of similarity between the averaged EP and the single-stimulus EEG. With electrical stimulation, the SNR is highest (0.41 +/- 0.21) for 1-12 stimuli and then significantly decreases to 0.2 +/- 0.08 for 13-24 stimuli (p < 0.001). With balloon distension (BD), the SNR is highest (0.22 +/- 0.16) for 1-12 stimuli and lowest (0.12 +/- 0.14) for 13-24 stimuli, but these SNRs are not significantly different from each other. Both electrical and mechanical stimulation of the oesophagus produce rapidly adapting EPs. The SNR of the EPs is higher with electrical stimulation than with BD. The EPs response to BD has a higher variability and is more noisy. Consequently, these results suggest that the overall cortical EP response to electrical stimulation of the oesophagus is more reproducible than that due to balloon distension.

Adult↗

PubMed1997

The magnitude of the central response to esophageal electrical stimulation is intensity dependent.

BACKGROUND & AIMS: Cerebral evoked potential (EP) responses to visceral stimulation represent a powerful method to assess visceral afferent pathways. The aim of this study was to establish basic stimulation parameters (dose-response relationship in EP amplitude and topographic brain organization) during electrical esophageal stimulation. METHODS: Electrical esophageal stimulation was performed in repeated series of 24 stimuli in 15 healthy subjects (25 years) by steps of 5 mA, ranging from 0.5 mA (sham) to 25 mA. EPs were obtained using scalp electrodes positioned according to the 10/20 International electroencephalographic system. Topographic EP maps were created using interpolation techniques. RESULTS: No cerebral responses were recorded with sham stimulation. A significant intensity-dependent increase of the major EP peaks (N1-P2) was observed between 5 and 25 mA (P < 0.05). A significant shortening of the mean peak latency of the first peak (N1) occurred with increasing stimulus intensity (P < 0.0001). Topographic brain maps localized the early EP peaks centrally, whereas later peaks were spread symmetrically over the centroparietal region. CONCLUSIONS: The clear dose-response relationship in the brain response with increasing stimulus intensities probably reflects increased recruitment of afferent fibers. Early peaks originate from deep central brain structures, whereas later peaks are localized exclusively in cortical regions.

Adult↗

PubMed1997

The cerebral response to electrical stimuli in the oesophagus is altered by increasing stimulus frequencies.

Recording of cerebral evoked responses (EP) allows the assessment of visceral afferent pathways and gut-brain communication, but the optimal stimulation parameters remain to be established. The present study determined the optimal stimulation frequency of electrical stimulation of the oesophagus to elicit EP responses. In 13 healthy male volunteers (24.1 +/- 5.9 years), a 5 mm stainless-steel electrode was placed in the distal oesophagus for electrical stimulation (ES). EP were recorded from 21 scalp electrodes placed according to the 10/20 International system. ES (15 mA, 200 microseconds) were delivered in repeated series of 24 stimuli. Stimulus frequency was randomly altered in different series using a pseudologarithmic range (0.1, 0.2, 0.3, 0.5, and 1 Hz). Two series of stimuli were applied using each stimulation frequency. Two-dimensional topographic brain maps were created using interpolation techniques at each stimulation frequency. With increasing stimulus frequency, a significant and progressive decrease of EP amplitudes was observed between frequencies of 0.1 Hz and 1.0 Hz (P1/N2: 7.6 +/- 1.2 vs 1.4 +/- 0.3* microV, N2/P2: 17.2 +/- 1.7 vs 4.6 +/- 0.4* microV, P2/N3: 6.9 +/- 0.7 vs 4.2 +/- 0.5* microV; * = P < 0.05). In addition, there was a significant shortening of the mean peak latency of the intercalated P2 peak (P < 0.0005), with a similar trend for the P3 peak (P < 0.06), with increasing stimulus frequency from 0.1-1.0 Hz. Topographic brain maps localized the maximal early peaks (N1,P1.N2) in the paracentral cortical region (C3, Cz, C4), whereas the later peaks (P2 to P3) were symmetrically spread over the centroparietal and temporal regions (Cz, Pz, T5, T4). There was no difference in the cortical location of maximal EP amplitudes with increasing stimulus frequency. In conclusion, there is a clear relationship between stimulus frequency and amplitude of EP, suggesting rapid attenuation of the cerebral autonomic neural responses with increased electrical stimulation frequency. The effect of increased frequency on peak latencies suggests an alteration of stimulus processing in the thalamocortical region due to an altered perception of stimuli. Early EP peaks originate from basal structures of primarily the dominant hemisphere, while later peaks are localized in centroparietal cortical regions.

Adult↗

PubMed1997

Cerebral abnormalities in patients with cirrhosis detected by proton magnetic resonance spectroscopy and magnetic resonance imaging.

Hepatic encephalopathy is a common problem in cirrhosis. The pathogenesis of this complication of advanced liver disease still remains unclear. Magnetic resonance spectroscopy was used to assess prospectively cerebral metabolism in 51 patients with histologically proven cirrhosis (Child-Pugh classes A, B, and C, 18, 18, and 15, respectively) and 36 healthy volunteers. According to the results of psychometric tests, overt hepatic encephalopathy, subclinical encephalopathy, and no encephalopathy were found in 14, 21, and 16 patients, respectively. Myoinositol/creatine ratios in gray (.36 +/- .17) and white (.35 +/- .22) matter voxel were reduced significantly (P < .0001) in cirrhotic patients compared with healthy volunteers (gray matter, .51 +/- .11; white matter, .64 +/- .16). In addition, patients showed a significant reduction (P = .024) in white matter choline/creatine ratio (.77 +/- .27) compared with controls (.92 +/- .25), and glutamine/glutamate level was elevated in cirrhotic patients compared with controls (gray matter, P < .0001; white matter, P = .036). Changes in cerebral myoinositol and glutamine/glutamate levels correlated significantly with the severity of hepatic encephalopathy (P < .0001). However, these metabolic alterations were also detected in patients without hepatic encephalopathy (normal psychometric test results). N-acetyl aspartate/creatine ratios did not differ between patients and controls. Magnetic resonance imaging detected bright basal ganglia in 37 patients, which correlated significantly with portal-systemic shunting and elevation of glutamine/glutamate, but not with the degree of hepatic encephalopathy. In conclusion, magnetic resonance imaging and spectroscopy showed that alterations of cerebral metabolism are common in patients with cirrhosis, even without evidence of clinical or subclinical hepatic encephalopathy.

Adult↗

PubMed1997

Imbalance of the interleukin 1 system in colonic mucosa--association with intestinal inflammation and interleukin 1 receptor antagonist [corrected] genotype 2.

BACKGROUND: Interleukin 1 (IL-1) alpha and beta are potent cytokines which play key roles in inflammation. They are controlled by IL-1 receptor antagonist (IL-1ra). AIMS: To investigate the influence of mucosal inflammation and IL-1ra genotype on the IL-1ra:IL-1 balance. PATIENTS AND METHODS: IL-1 alpha, IL-1 beta, and IL-1ra were measured by enzyme linked immunosorbent assay (ELISA) in biopsy specimens taken from inflamed and non-inflamed colon of 60 patients with Crohn's disease (CD), 34 with ulcerative colitis (UC), 15 inflammatory controls, and 103 non-inflamed controls. IL-1ra genotype was determined by polymerase chain reaction and gel electrophoresis. RESULTS: IL-1 alpha and IL-1 beta were significantly increased in inflamed mucosa in inflammatory bowel disease (IBD) (CD: 53.5 (22.4) and 409.9 (118.7) pg/mg protein, respectively; UC: 18.9 (6.8) and 214.5 (78.2) pg/mg, respectively) and non-IBD patients (19.2 (7.4) and 281.4 (121.0) pg/mg, respectively; p < 0.0001) compared with normal controls (2.8 (0.6) and 30.6 (5.6) pg/mg, respectively). In CD IL-1 alpha and beta were also significantly increased in non-inflamed mucosa (6.1 (1.3) pg/mg and 88.7 (17.4) pg/mg, respectively; p < 0.0012). IL-1ra:(IL-1 alpha+beta) ratios were significantly decreased in inflamed mucosa of patients with CD (182 (45); p < 0.0001), UC (425 (136); p = 0.0018) and without IBD (221 (76); p < 0.0001), and in non-inflamed mucosa in CD (369 (149); p < 0.0001) compared with normal controls (1307 (245); p < 0.0001). Patients with IL-1ra genotype 2 had slightly but significantly reduced mucosal IL-1ra concentrations (p = 0.003). The greatest difference was seen in colonic biopsy specimens from patients with inflamed Crohn's disease. CONCLUSION: Mucosal inflammation can modulate the balance of the IL-1:IL-1ra system in colonic mucosa.

Adult↗

PubMed1997

Neurocardiac response to esophageal electric stimulation in humans: effects of varying stimulation frequencies.

The purpose of this study was to determine if the cardioautonomic responses to esophageal electric stimulation were mediated entirely through modulation of respiratory frequency or a direct vagal effect. We performed electric stimulation of the esophagus in 13 healthy male controls (24 +/- 6 yr) using a manometric catheter to which a stainless steel electrode was attached. Stimulation frequencies ranged from 0.1 to 1 Hz and were applied in random fashion. We computed the power spectra of the heart rate variability and respiratory frequency as measures of autonomic function. Electric stimulation of the esophagus produced significant increases in the high-frequency power of the heart rate autospectrum at all stimulation frequencies (maximal at 0.2 Hz). However, regardless of the frequency of esophageal stimulation, the respiratory rate was not changed from baseline. These studies indicate that enhancement of cardiac vagal modulation observed in response to esophageal electric stimulation is not primarily due to changes in respiratory frequency, but rather occurs through a direct, vagally mediated action through sensory neural pathways involving vagal esophageal afferents.

Adult↗