Biomedical subjects

P Enck

Publications and source records attributed to P Enck.

At least 19 recordsLinked to original sources

PubMed2006

Passenger well-being in airplanes.

Passenger well-being is influenced by cabin environmental conditions which interact with individual passenger characteristics like age and health conditions. Cabin environment is composed of different aspects, some of which have a direct influence on gastrointestinal functions and may directly generate nausea, such as cabin pressure, oxygen saturation, and motion or vibration. For example, it has been shown that available cabin pressure during normal flight altitude can significantly inhibit gastric emptying and induce dyspepsia-like symptoms when associated with a fibre-rich meal. Other aspects of the cabin environment such as space and variability of seating, air quality, and noise, also have been shown to modulate (reduce or increase) discomfort and nausea during flights. Individual passenger characteristics and health status also have been demonstrated to increase vulnerability to adverse health outcomes and discomfort.

Air Pollution, Indoor↗

PubMed2006

STW 5 (Iberogast) reduces afferent sensitivity in the rat small intestine.

INTRODUCTION: A limited number of drugs are available for the treatment of functional dyspepsia and irritable bowel syndrome. The efficacy of STW 5 (Iberogast) was previously shown in clinical trials. Since visceral hypersensitivity seems to be the prime pathomechanism of functional gastro-intestinal disorders, the aim of this study was to explore whether STW 5 reduces intestinal afferent sensitivity in the upper gastrointestinal tract. METHODS: Two groups of male Wistar rats were pretreated with either the herbal preparation STW 5 or its vehicle (30.8% ethanol). Then, after 2h, general anesthesia was induced by pentobarbitone (60 mg kg(-1)i.p.) and extracellular multi-unit afferent recordings were obtained from mesenteric afferents innervating the proximal jejunum. The intestinal afferent nerve response to increasing doses of 5-HT and bradykinin were quantified as well as afferent discharge following a ramp distension of the adjacent intestinal loop from 0 to 60 cm H(2)O. RESULTS: Afferent discharge to 5-HT and bradykinin increased dose-dependently. Following the different doses of 5-HT, the peak in afferent nerve discharge was always reduced after pretreatment with STW 5 compared to controls with a response of 110+/-5 imp s(-1) after STW 5 and 128+/-3 in vehicle controls at the maximum dose (40 microg kg(-1); p<0.05; mean+/-SEM). For bradykinin, afferent responses were reduced following STW 5 at the 20 and 40 microg kg(-1) dose but not at 10 microg kg(-1) (40 microg kg(-1)176+/-7 imp s(-1) following STW 5 versus 200+/-6 imp s(-1) in controls; p<0.05). The ramp distension of the intestinal loop stimulated a rise in intestinal afferent nerve discharge that was always lower in the STW 5 pretreated group compared to vehicle controls with the exception of the discharge rate at the pressure level of 0 and 20 cm H(2)O (all other pressures up to 60 cm H(2)O p<0.05). CONCLUSIONS: Sensitivity of intestinal afferents to mechanical and chemical stimuli is reduced following treatment with the herbal preparation STW 5. This mechanism may help to explain why STW 5 relieves dyspeptic and bowel symptoms in patients.

Afferent Pathways↗

PubMed2006

[Placebo response in functional bowel disorders].

The placebo response in functional bowel disorders is incompletely understood, and is usually either mystified or down-played; a rational approach to the understanding of the placebo response, however, can be deduced from the scientific literature. We present 3 theories that may explain most of the placebo response in medical and psychological interventions. a) Regression to the Mean (RTM): This refers to "errors" in measuring the outcome of therapies that are due to small samples sizes, global assessment variables, spontaneous variability of symptoms, and other methodological reasons. b) Pavlovian Conditioning (PC): Here the placebo response occurs as the consequence of successful association of diagnostic and therapeutic procedures in the past (illness history) of the individual that resulted in symptom improvement. Stimuli in the context of a treatment can thus gain therapeutic potency (become conditioned stimuli), e. g., the procedure of an injection or the colour of a drug. c) Signal Detection theory (SDT): Manipulation of expectations and cognitions of the patient by suggestions and verbal instructions of the health-care system will change the willingness of the patient to perceive symptoms as improved/worsened, specifically if this happens under "noisy" circumstances, e. g., with high spontaneous variability of symptoms. All three models are illustrated with examples from the medical and psychological treatments or experiments, including recent findings of cortical correlates of the placebo response in functional brain imaging investigations. Potential biological mechanisms for the placebo response are discussed, including he possibility of the genetic predisposition to be a placebo responder.

Clinical Trials as Topic↗

PubMed2005

Functional imaging of stress urinary incontinence.

Stress urinary incontinence (SUI) is defined as an involuntary loss of urine during increases in intraabdominal pressure such as coughing or laughing. It is often a consequence of weakness of the pelvic floor. Treatment of SUI consists of pelvic floor muscle training with EMG-biofeedback (PFMT) or contraction-exercises, with voluntary pelvic contractions in order to strengthen the pelvic floor. We investigated neuroplastic changes comparing PFMT with EMG-biofeedback before and after training in ten female patients with SUI using event-related functional Magnetic Resonance Imaging (fMRI). After a 12-week training a more focused activation in the primary motor and somatosensory cortical representation sites of the lower urogenital tract was found. In addition, reductions in brain activation in the insula, right frontal operculum and the anterior cingulate cortex suggest changes in emotional arousal in micturition after treatment. These changes are related to clinical improvement documented by decreased number of incontinence episodes and increased EMG-activity of the pelvic floor muscles after training. The changes in EMG-activity were correlated with heightened BOLD responses in the primary motor and primary sensory cortical representation sites of the lower urogenital tract.

Adult↗

PubMed2005

Acupuncture treatment in irritable bowel syndrome.

BACKGROUND AND AIMS: Despite occasional positive reports on the efficacy of acupuncture (AC) on functions of the gastrointestinal tract, there is no conclusive evidence that AC is effective in the treatment of irritable bowel syndrome (IBS). PATIENTS AND METHODS: Forty three patients with IBS according to the Rome II criteria were randomly assigned to receive either AC (n = 22) or sham acupuncture (SAC) (n = 21) using the so-called "Streitberger needle". Treatment duration was 10 sessions with an average of two AC sessions per week. The primary end point was improvement in quality of life (QOL) using the functional digestive diseases quality of life questionnaire (FDDQL) and a general quality of life questionnaire (SF-36), compared with baseline assessments. QOL measurements were repeated three months after treatment. RESULTS: Both the AC and SAC groups improved significantly in global QOL, as assessed by the FDDQL, at the end of treatment (p = 0.022), with no differences between the groups. SF-36 was insensitive to these changes (except for pain). This effect was partially reversed three months later. Post hoc comparison of responders and non-responders in both groups combined revealed a significant prediction of the placebo response by two subscales of the FDDQL (sleep, coping) (F = 6.746, p = 0.003) in a stepwise regression model. CONCLUSIONS: Acupuncture in IBS is primarily a placebo response. Based on the small differences found between the AC and SAC groups, a study including 566 patients would be necessary to prove the efficacy of AC over SAC. The placebo response may be predicted by high coping capacity and low sleep quality in individual patients.

Acupuncture Therapy↗

PubMed2005

[Determination of placebo effect in irritable bowel syndrome].

BACKGROUND AND OBJECTIVE: The determinants of the placebo effect are not well established. Goal of this study was to explore likely predictive factors in an already published data set. METHODS: We re-analysed data from a study in 120 patients with the irritable bowel syndrome (IBS) that were randomly assigned to three arms of the study to receive (double-blind) either a drug (mebeverin) (n = 40) or placebo (n = 40), or (in an open trial) dietary treatment (fibre) (n = 40) for up to 16 week. Treatment was conducted by 3 different doctors (A, B, C) with 44, 27, and 18 patients, resp. A fourth group (n = 31) was treated by different varying physicians. Symptoms were assessed every 4 weeks, and the degree of patient compliance and the number of drop-outs, the number of patients improved/not improved (in %), symptom severity (Kruis Score) at enrolment, and age and gender as covariates were included into the analysis. RESULTS: Drop-out rate was 30 % for placebo, 30 % for mebeverin, and 15 % for the diet. For the patients remaining in the study, average compliance was 75 % with placebo, but 89 % for the drug and 82 % for the diet. Response rates were 39 % for placebo, but 20 % for the drug; response rate for the diet (open trial) was 43 % under all doctors. Response rates for drug and placebo combined were 32 % for doctor A (female,43 years), but 19 % for doctors B and C together (both males, 32 and 40 years)); this effect was not significant. Placebo responders were more often women (47 %) than men (28 %), while age effects were only found with dietary treatment: responders were younger. Placebo responders had an overall lower Kruis Score than non-responders (45 vs 52 points), but this was also true for drug (52 vs. 62 points) and diet responders (56 vs 68 points). CONCLUSION: The major factors contributing to the placebo response are the treating physician (gender, training), and the patients gender (female). Patients with lower Kruis score (more likely non-functionally disordered) may be prone to higher (placebo) response rates.

Adult↗

PubMed2005

Lipopolysaccharide-induced changes in mesenteric afferent sensitivity of rat jejunum in vitro: role of prostaglandins.

Bacterial translocation across the intestinal mucosal barrier leads to a macrophage-mediated inflammatory response, visceral hyperalgesia, and ileus. Our aim was to examine how mediators released into mesenteric lymph following LPS treatment influence intestinal afferent sensitivity and the role played by prostanoids in any sensitization. Intestinal lymph was collected from awake rats following treatment with either saline or LPS (5 mg/kg ip). Extracellular multiunit afferent recordings were made from paravascular mesenteric nerve bundles supplying the rat jejunum in vitro following arterial administration of control lymph, LPS lymph, and LPS. Mesenteric afferent discharge increased significantly after LPS lymph compared with control lymph. Peak discharge occurred within 2 min and remained elevated for 5 to 8 min. This response was attenuated by pretreatment with naproxen (10 microM), and restored upon addition of prostaglandin E(2) (5 microM) in the presence of naproxen, but AH6809 (5 microM), an EP(1)/EP(2) receptor(s) antagonist, failed to decrease the magnitude of LPS lymph-induced response. LPS itself also stimulated mesenteric afferent discharge but was unaffected by naproxen. TNF-alpha was significantly increased in LPS lymph compared with control lymph (1,583 +/- 197 vs. 169 +/- 38 pg/ml, P < 0.01) but exogenous TNF-alpha failed to evoke any afferent nerve discharge. We concluded that inflammatory mediators released from the gut into mesenteric lymph during endotoxemia have a profound effect on afferent discharge. These mediators influence afferent firing via the release of local prostaglandins.

Animals↗

PubMed2005

The external anal sphincter and the role of surface electromyography.

Assessment of the neuronal control of the external anal sphincter (EAS) has long been restricted to investigating patients with defecation disorders by invasive tools such as needle electromyography (EMG), while less invasive techniques have been regarded as non-suitable for diagnostic purposes. Multichannel surface EMG by means of electrode arrays applied to anal sphincter muscle records and identifies individual motor unit action potentials, their place of origin along the circumference, their repetitive firing frequency, and their progression along the muscle fibres at different levels within the anal canal. These data shed doubts on conventional knowledge about the anatomy of the EAS muscle, and confirms new concepts of anatomical differences between gender. This may eventually be transferred to a new understanding of the role of symmetry and asymmetry of pelvic floor innervation and its role in the pathogenesis of fecal incontinence.

Adult↗

PubMed2005

The puborectalis muscle.

The role of the levator ani and puborectalis muscle in preserving continence has been underestimated in the past, due predominantly to technical difficulties to investigate its proper function in healthy subjects, and its dysfunction as in patients with incontinence problems. This has recently been overcome by applying new investigational procedures such as a perineal dynamometer which measures the traction exerted by the levator ani on an intrarectal balloon catheter, or by multi-electrode arrays recording the generation of motor unit action potentials from various parts of the puborectalis muscle sling via intrarectal surface electrodes. Both techniques have the potential to provide new insights into the physiology of defecation and the pathophysiology of incontinence and constipation.

Anal Canal↗

PubMed2005

The placebo response in functional bowel disorders: perspectives and putative mechanisms.

The nature and determinants of the placebo response are widely unknown, as are the underlying psychological and biological mechanisms. High placebo response rates in functional bowel disorders (functional dyspepsia, irritable bowel syndrome) are similar to those in non-intestinal diseases (depression, pain, Parkinson's disease) and not too dissimilar to other organic gastrointestinal diseases (duodenal ulcer, inflammatory bowel diseases). Methodological reasons (regression to the mean, shift in signal detection through manipulation of expectations) and psycho-biological mechanisms (Pavlovian conditioning of biological processes) are proposed to explain a large component of the response variance in clinical trials. Psychobiological mechanisms of the placebo response in functional and organic diseases can also be identified in brain function studies (such as imaging).

Gastrointestinal Diseases↗

PubMed2004

Multichannel surface EMG for the non-invasive assessment of the anal sphincter muscle.

BACKGROUND/AIMS: This work focuses on recording, processing and interpretation of multichannel surface EMG detected from the external anal sphincter muscle. The aim is to describe the information that can be extracted from signals recorded with such a technique. METHODS: The recording of many signals from different locations on a muscle allows the extraction of additional information on muscle physiology and anatomy with respect to that obtained by classic bipolar recordings. Multichannel EMG methods have been recently developed for the assessment of the external anal sphincter. An anal probe was used in this study to record signals at different depths within the anal canal during contractions at different effort levels. The plug is 150 mm in length and 14 mm in diameter, holding a circumferential array of 16 equally spaced silver bar electrodes, located at a distance of 20 mm from the probe tip and aligned with the probe axis. RESULTS: Information about localization of the innervation zone, fiber length, EMG amplitude, muscle fiber conduction velocity and single motor unit analysis can be obtained from the signals recorded with the circumferential array by means of innovative signal processing techniques. CONCLUSIONS: The type of information extracted from multichannel surface EMG signals cannot be obtained with other currently available techniques. The technological innovation described in this work is promising for a further insight into the investigation of pelvic floor pathologies and rehabilitation treatments.

Anal Canal↗

PubMed2004

Innervation zones of the external anal sphincter in healthy male and female subjects. Preliminary results.

OBJECTIVES: The objective of this work was to investigate the distribution of the innervation zones of the motor units that make up the external anal sphincter (EAS) in healthy males and females. METHODS: A cylindrical probe carrying a circumferential array of 16 electrodes was used to detect the generation, propagation and extinction of individual motor unit action potentials (MUAPs) at 1, 2, and 3 cm depth from the orifice of the anal canal during maximal voluntary contractions of the EAS. Fifteen healthy males and 37 healthy nulliparous females were investigated. RESULTS: IZs could be detected in all males and in 34 out of 37 females. In the males, the IZs are scattered in the right and left hemisphincter at each of the three levels and their distribution is not affected by depth. In the females, the distribution is also concentrated in the right and left hemisphincter at depth 1 cm but is more uniform at depth 2 cm and more concentrated in the dorsal and ventral regions at depth 3 cm. ANOVA shows a statistically significant dependence of the IZ distribution on depth only in females and not in males. CONCLUSIONS: It is concluded that (a) IZs of the EAS can indeed be detected with a circumferential array placed at different depths along the anal canal; (b) large individual variability is observed, and (c) IZs show similar distribution at the three depth levels in males and different distributions in females.

Adult↗

PubMed2004

The herbal preparation STW 5 (Iberogast) desensitizes intestinal afferents in the rat small intestine.

INTRODUCTION: Visceral hypersensitivity in the upper gastrointestinal tract is a potential pathomechanism of functional dyspepsia. The herbal preparation STW 5 (Iberogast) provides symptomatic relief for this condition. We aimed to investigate whether STW 5 modulates intestinal afferent sensitivity. METHODS: The herbal preparation STW 5 or vehicle (30.8% ethanol) were administered orally in male Wister rats. After 2 h animals were anaesthetized and extracellular multi-unit intestinal afferent nerve recordings were secured from the neurovascular bundle of the mesentery in the proximal jejunum. Afferent discharge to ramp distension of the intestinal loop (0-60 cm H2O) and dose-response curves for i.v. bradykinin (10, 20 and 40 microg kg(-1)) and 5-HT (5, 10, 20 and 40 microg kg(-1)) were recorded. RESULTS: Baseline discharge was not different between the vehicle and treatment group. Ramp distension was followed by a pressure dependent increase in afferent nerve discharge that was decreased following STW 5 pretreatment for all distending pressures reaching 147 +/- 8 impulses s(-1) (imp s(-1)) following STW 5 vs 171 +/- 5 imp s(-1) following vehicle at 60 cm H2O (mean +/- SEM; P < 0.05). A dose-dependent increase in afferent discharge was observed for 5-HT and bradykinin. Following STW 5 pretreatment, afferent discharge was reduced at all doses of 5-HT to 110 +/- 5 at the maximum dose after STW 5 and 128 +/- 3 imp s(-1) in controls (all P < 0.05). Afferent discharge to bradykinin was similarly reduced at 20 and 40 microg kg(-1) but not at 10 microg kg(-1) of bradykinin with a discharge rate of 176 +/- 7 imp s(-1) following STW 5 and 200 +/- 6 imp s(-1) in controls at 40 microg kg(-1) (P < 0.05). CONCLUSIONS: The preparation STW 5 reduces intestinal afferent nerve discharge following chemical and mechanical stimuli, while baseline discharge is not affected. This effect of STW 5 on afferent sensitivity may contribute to its therapeutic relief of dyspeptic symptoms.

Animals↗

PubMed2004

Capasaicin induced deafferentation enhances the effect of electrical vagal nerve stimulation on food intake and body mass.

Study was based on hypothesis that electrical stimulation (ES) with parameters obtained from analysis of vagal afferent discharge fed state may fake brain with satiety state. We evaluated effect of denervation of vagal capsaicin-sensitive afferents on food intake and body weight in rats with ES of vagal nerves using microchip (MC). Group A was scheduled to MC implantation, B to sham operation only, C to MC implantation and capsaicin vagal deafferentation, and D to capsaicin denervation only. ES lasted 24 days. MC parameters were 0.05 Hz, 0.1s, 0.55 V. ES of left vagus significantly reduced total food intake as well as the mean daily intake in groups A and C in comparison to control and D group (ANOVA, F=18.55, p=0.0038). Body weight was lower in group A (3462 g) and C (2727 g) then in control (3814 g) and D (3568 g) (F=25.68, p=0.00068). Leptin decreased in C (165 pg/mL) in comparison to A (625 pg/mL), B (677 pg/mL), and D (612 pg/mL) (p<0,05), mainly due to ES (F=7.27, p=0.019). Glucose was decreased in A (F=5.55, p=0.036) - by 11% and by 16% in C group. Proper vagal neuromodulation results in central and peripheral effects causing food intake and body weight downregulation.

Administration, Topical↗

PubMed2003

Stress-induced attenuation of brain stem activation following intestinal anaphylaxis in the rat.

Intestinal anaphylaxis triggers neuronal activation in the nucleus tractus solitarius (nTS) of the rat brain stem. Stress may modulate reflex circuitry in the brain stem and facilitate intestinal inflammatory responses. We hypothesized that stress would modulate central neuronal activation during intestinal anaphylaxis. NTS neurons were activated following intestinal antigen challenge in sensitized Hooded Lister rats but not in negative controls (P < 0.05). The number of Fos-positive neurons following intestinal anaphylaxis decreased in animals exposed to water-avoidance stress (P < 0.05), although serum levels of rat mast cell protease II were not different in stressed and unstressed animals, indicating a similar degree of mast cell degranulation. Stress seems to inhibit neuronal activation in the rat brain stem during intestinal inflammation without modulation of the inflammatory response itself. This may have implications for a potential efferent neuronal modulation of inflammatory responses in the gut.

Anaphylaxis↗

PubMed2003

Measurement of gastric emptying by 13C-octanoic acid breath test versus scintigraphy in diabetics.

In this prospective study, we compared the assessment of gastric emptying by the 13C-octanoic acid breath test to gastric emptying scintigraphy in diabetics. We also examined the relationship between gastric emptying parameters and gastric symptoms and cardiovascular autonomic function. The 13C-octanoic acid breath test and scintigraphy were performed simultaneously in 24 diabetics with a solid test meal (1 egg, doubly labelled with 91 mg 13C-octanoic acid and 50 MBq 99mTechnetium-Nanocoll, 60 g white bread, 5 g margarine and 150 ml water). At fifteen-minute intervals, breath samples were taken over 4 hours and examined by mass spectrometry. In parallel, scintigraphy was performed for 2 hours at one minute intervals. Using breath test data, gastric emptying half time (t (1/2) ), lag-phase (t lag ) and gastric emptying coefficient (GEC) were calculated. Subsequently, the correlation of these results with the equivalent data from scintigraphy were determined employing a regression method. To detect a cardiovascular autonomic neuropathy, a 24-h ECG recording was performed. The prevalence of gastrointestinal symptoms in our collective was assessed by a standardized questionnaire. There was a highly significant positive correlation of both 13C-octanoic acid breath test t (1/2) and scintigraphic t (1/2) (r = 0.8257; p < 0.0001) and 13C-octanoic acid breath test t lag and scintigraphic t lag (r = 0.6302; p < 0.001). The sensitivity of the 13C-octanoic acid breath test was 1 and the specificity was 0.73. In our study, there was no significant association of cardiovascular and gastrointestinal autonomic neuropathy. Furthermore, there was no significant relationship between the prevalence of gastrointestinal symptoms and gastric emptying disorders. We conclude that the 13C-octanoic acid breath test represents a suitable method to measure disordered gastric emptying in diabetics due to its highly significant positive correlation to scintigraphy and due to its validity. It is not possible to predict diabetic gastroparesis on the basis of other autonomic function disorders or because of dyspeptic symptoms.

Adult↗

PubMed2002

Influences of pelvic floor structures and sacral innervation on the response to distension of the cat rectum.

The contributions to the rectal response to distension of the pelvic floor structures surrounding the rectum and of the sacral spinal innervation have never been studied. Using paralysed intercollicularly decerebrate, anaesthesia-free cats, we studied pressure-volume relationships during slow ramp distensions of the rectum. Results obtained from animals with intact pelvic cavities were compared with those following mobilization of the rectum from the pelvic floor musculature. To assess the influences of spinal outflow and afferent input, rectal pressure-volume relationships were measured in the mobilized rectum following bilateral sequential transection of the spinal roots S1 to S3, first dorsal, then ventral. Isolation of the rectum from the pelvic floor structures resulted in a decrease in balloon volume in the lower range of distension pressure but did not affect volumes at higher pressures. The only afferent effect was seen after sectioning of dorsal roots S1, which resulted in a decrease in balloon volume. The only efferent effect was seen after sectioning of ventral roots S3, which decreased balloon volume further. In conclusion, the rectal response to distension depends on the properties of the rectal wall. It may be influenced by somatic inputs, inputs from the myenteric nervous plexus, and from the parasympathetic and sympathetic nervous systems. Afferent inputs and spinal autonomic reflexes may decrease the tone of the rectal musculature during distension.

Animals↗

PubMed2002

Serotonin type-4 receptors modulate the sensitivity of intramural mechanoreceptive afferents of the cat rectum.

It has been suggested that serotonin (5-hydroxytryptamine) type-4 (5-HT4) receptors modulate the sensitivity of intrinsic afferents of the intestinal mucosa. We studied the involvement of 5-HT4receptors in the modulation of extrinsic afferent sensitivity of the intestinal wall. During distension ramps, mechanoreceptive rectal afferents in sacral dorsal roots were examined in decerebrate anaesthesia-free cats using the selective 5-HT4receptor partial agonist, tegaserod (HTF 919), and the 5-HT4receptor antagonist, SB 203186. The static discharge rate of the afferents evoked by rectal distension decreased after intravenous (i.v.) administration of tegaserod at intraluminal pressures above 30 mmHg, with the most effective reduction occurring at 50 mmHg. The effect was dose-dependent, with maximal reduction occurring at 1.2 mg kg-1 bodyweight, and could be partly reversed by i.v. administration of SB 203186. Tegaserod did not alter the pressure-volume relationship (compliance) of the rectum. It is tentatively concluded that 5-HT4receptor activation has an inhibitory effect on intramural mechanoreceptors in the cat's rectum. Our results are in line with the observation that tegaserod relieves the sensory symptoms of patients suffering from irritable bowel syndrome.

Animals↗