Population-based study of surgical treatment with and without tumour resection in patients with locally recurrent rectal cancer.

BACKGROUND: Population-based studies of treatment of locally recurrent rectal cancer (LRRC) are lacking. The aim was to investigate the surgical treatment of patients with LRRC at a national population-based level. METHODS: All patients undergoing abdominal resection for primary rectal cancer between 1995 and 2002 in Sweden with LRRC as a first event were included. Detailed information about treatment, complications and outcomes was collected from the medical records. The patients were analysed in three groups: patients who had resection of the LRRC, those treated without tumour resection and patients who received best supportive care only. RESULTS: In all, 426 patients were included in the study. Of these, 149 (35·0 per cent) underwent tumour resection, 193 (45·3 per cent) had treatment without tumour resection and 84 (19·7 per cent) received best supportive care. Abdominoperineal resection was the most frequent surgical procedure, performed in 65 patients (43·6 per cent of those who had tumour resection). Thirteen patients had total pelvic exenteration. In total, 63·8 per cent of those whose tumour was resected had potentially curative surgery. After tumour resection, 62 patients (41·6 per cent) had a complication within 30 days. Patients who received surgical treatment without tumour resection had a lower complication rate but a significantly higher 30-day mortality rate than those who underwent tumour resection (10 versus 1·3 per cent respectively; P = 0·002). Of all patients included in the study, 22·3 per cent had potentially curative treatment and the 3-year survival rate for these patients was 56 per cent. CONCLUSION: LRRC is a serious condition with overall poor outcome. Patients undergoing curative surgery have an acceptable survival rate but substantial morbidity. There is room for improvement in the management of patients with LRRC.

Population-based study of factors predicting treatment intention in patients with locally recurrent rectal cancer.

BACKGROUND: Local recurrence of rectal cancer (LRRC) is associated with poor survival unless curative treatment is performed. The aim of this study was to investigate predictive factors for treatment with curative intent in patients with LRRC. METHODS: Population-based data for patients treated for primary rectal cancer between 1995 and 2002, and with LRRC reported as first event were collected from the Swedish Colorectal Cancer Registry and medical records. The associations between patient-, primary tumour- and LRRC-related factors and intention of the treatment for LRRC were determined. The impact of the identified predictive factors on prognosis after treatment with curative intent was also assessed. RESULTS: A total of 426 patients were included in the study, of whom 149 (35·0 per cent) received treatment with curative intent. Factors significantly associated with treatment of the LRRC with palliative intent were primary surgery with abdominoperineal resection (odds ratio (OR) 5·16, 95 per cent c.i. 2·97 to 8·97), age at diagnosis of LRRC at least 80 years (OR 4·82, 2·37 to 9·80), symptoms at diagnosis (OR 2·79, 1·56 to 5·01) and non-central location of the LRRC (OR 1·79, 1·15 to 2·79). The overall 5-year survival rate was 8·9 per cent for all patients and 23·1 per cent among those treated with curative intent. In patients treated with curative intent, factors associated with increased risk of death were age 80 years or more (hazard ratio (HR) 2·44, 95 per cent c.i. 1·55 to 3·86), presence of symptoms (HR 1·92, 1·20 to 3·05), non-central tumour location (HR 1·51, 1·01 to 2·26) and presence of hydronephrosis (HR 2·02, 1·18 to 3·44). CONCLUSION: Non-central location of the LRRC, presence of symptoms and age at least 80 years at diagnosis of the LRRC were associated with treatment with palliative intent.

Carbon monoxide: its role in photochemical smog formation.

The photochemistry of trace amounts of isobutene and oxides of nitrogen in an atmosphere of air was studied both in the presence and in the absence of small amounts of carbon monoxide. Carbon monoxide accelerates the reaction as measured by nitric oxide oxidation or ozone formation. This finding has relevance to photochemical smog formation.

Sterile soil from Antarctica: organic analysis.

Soils from the dry-valley region of Antarctica can be sterile by the usual microbiological criteria and yet contain significant amounts of organic carbon. Examination of one such soil shows that the organic material is finely divided anthracite coal. These findings have significant implications for the biological exploration of Mars.

Brainstem mechanisms underlying feeding behaviors.

The essential elements controlling trigeminal motoneurons during feeding lie between the trigeminal and facial motor nuclei. These include populations of neurons in the medial reticular formation and pre-motoneurons in the lateral brainstem that reorganize to generate various patterns. Orofacial sensory feedback, antidromic firing in spindle afferents and intrinsic properties of motoneurons also contribute to the final masticatory motor output.

Time to local recurrence as a prognostic factor in patients with rectal cancer.

AIMS: Survival after the local recurrence of rectal cancer is influenced by several factors. The aim of this study was to ascertain whether the time interval from primary surgery for rectal cancer to local recurrence diagnosis has any impact on survival. METHODS: Population-based data was collected from the Swedish Colorectal Cancer Registry. 7410 patients were operated with radical abdominal surgery for rectal cancer during the period 1995-2002. Of these, 386 (5%) developed a local recurrence as a first event. The patients were divided into two groups: early local recurrence (ELR), diagnosed <12 months after primary surgery, and late local recurrence (LLR), diagnosed ≥12 months after primary surgery. Kaplan-Meier curves and hazard ratios were calculated for survival analyses. Survival was calculated from the date of the local recurrence diagnosis to death or end of follow-up. RESULTS: Ninety-five patients had ELR and 291 patients LLR. Median time to local recurrence was 1.7 (0.1-7.9) years. Patients with a stage III primary tumour and non-irradiated patients were more common in the ELR compared with the LLR group. Factors that influenced survival were age at diagnosis of local recurrence (p < 0.001), stage of primary tumour (p = 0.027), and surgical resection of local recurrence (p < 0.001). Time to diagnosis of local recurrence had no influence on survival. CONCLUSIONS: No difference in survival from date of diagnosis of local recurrence was seen between patients with ELR and patients with LLR. All patients with local recurrence should therefore be assessed for potential curative surgery, disregarding time to local recurrence.

Anatomical organization of efferent neurons innervating various regions of the rabbit masseter muscle.

Previous studies have shown that the masseter muscle is supplied by motoneurons located in the anterodorsal region of the trigeminal motor nucleus and by an additional group of efferent neurons located in cell group k. The present experiments were performed on nine rabbits and were designed to establish the locations of neurons innervating the different regions of this muscle. Retrograde labeling with two fluorescent tracers (FluoroGold and Fast Blue) was applied to the central ends of cut branches of the masseter nerve. Serial coronal sections of the brainstem were viewed with fluorescence microscopy. The labeled cells were counted in all animals, and three-dimensional reconstructions of their distribution were made in five cases. In each successful experiment, labeled neurons were seen in the anterodorsal region of the trigeminal motor nucleus and in the two dorsal cell columns of cell group k (k1 and k3). Within-animal comparisons of the median position of populations innervating two distinct muscle regions in five rabbits showed that there were no significant differences in either the dorsoventral or rostrocaudal axes. However, in each case, there was a small but significant difference (83-173 microm) in the mediolateral axis within the motor nucleus but not within cell group k. Even in this axis, there was a 94-99% overlap of the two populations. Comparisons of the neuronal cross-sectional area showed that the deep regions were innervated by a larger proportion of small neurons from both nuclei than were the superficial and intermediate regions. Our results suggest that there is no simple topographical arrangement of motoneurons that corresponds to the peripheral pattern of nerve supply to the different regions of the masseter muscle.

Distribution of cholinergic neurons in cell group K of the rabbit brainstem.

The cell bodies of efferent neurons supplying the masseter and digastric muscles of the rabbit are located in two brainstem nuclei: the trigeminal motor nucleus and cell group k. The latter also contains neurons innervating muscles of the middle ear and Eustachian tube, as well as neurons that project to the cerebellum and the oculomotor complex. As part of an attempt to identify the functional subpopulations within the three cell divisions (kl-k3) that make up cell group k, we have investigated the distribution of neurons containing choline acetyltransferase, because these are likely to be motoneurons. Five rabbits anaesthetized with sodium pentobarbital (90 mg/kg, i.v.) were used in this study. They were perfused with 4% paraformaldehyde and 0.1% glutaraldehyde in phosphate buffer (0.1 M, pH 7.4). Two animals were used for preliminary studies. In the other three cases, serial Vibratome coronal sections of the brainstem were cut at 50 microm and two series of alternating sections were collected. The first was stained with a monoclonal antibody (code AB8, Incstar) directed against choline acetyltransferase, using the avidin-biotin-peroxidase method. The other was stained with Cresyl Violet. Cell counts and three-dimensional reconstructions were made for both series to determine positions and ratios of cholinergic and non-cholinergic neurons within the trigeminal motor nucleus and the subdivisions of cell group k. The results showed that the numbers of choline acetyltransferase- and Nissl-stained neurons within the trigeminal motor nucleus were almost identical. In cell group k, significantly fewer choline acetyltransferase-stained cells were counted in all three animals (ratios of choline acetyltransferase/Nissl=0.53-0.71). In addition, the distribution of cholinergic neurons was not uniform throughout cell group k. Subdivisions kl and k3 contained proportionately fewer choline acetyltransferase-positive cells (ratios of choline acetyltransferase/Nissl=0.23-0.64) than did k2 (ratios choline acetyltransferase/ Nissl=0.75-0.88). Within each subdivision, there were significant differences in the spatial coordinates of Nissl- and choline acetyltransferase-positive neurons. We conclude that cell group k contains at least two populations of neurons which are unevenly distributed between and within the three subdivisions. While the majority of neurons in subgroup k2 contain choline acetyltransferase and thus are likely to be motoneurons, more than half of the neurons in subgroups k1 and k3 are not cholinergic. It remains to be determined whether these are the neurons that project to the cerebellum and to other CNS regions.

Identification of brainstem interneurons projecting to the trigeminal motor nucleus and adjacent structures in the rabbit.

Neurons of several nuclei within the medial pontomedullar reticular formation are active during mastication, but their relationship with other elements of the pattern generating circuits have never been clearly defined. In this paper, we have studied the connection of this area with the trigeminal motor nucleus and with pools of last-order interneurons of the lateral brainstem. Retrograde tracing techniques were used in combination with immunohistochemistry to define populations of glutamatergic and GABAergic neurons. Injections of tracer into the Vth motor nucleus marked neurons in several trigeminal nuclei including the ipsilateral mesencephalic nucleus, the contralateral Vth motor nucleus, the dorsal cap of the main sensory nucleus and the rostral divisions of the spinal nucleus bilaterally. Many last-order interneurons formed a bilateral lateral band running caudally from Regio h (the zone surrounding the Vth motor nucleus), through the parvocellular reticular formation and Vth spinal caudal nucleus. Injections of tracer into Regio h, an area rich in last-order interneurons, marked, in addition to the areas listed above, a large number of neurons in the medial reticular formation bilaterally. The major difference between injection sites was that most neurons projecting to the Vth motor nucleus were located laterally, whereas most of those projecting to Regio h were found medially. Both populations contained glutamatergic and GABAergic neurons intermingled. Our results indicate that neurons of the medial reticular formation that are active during mastication influence Vth motoneurons output via relays in Regio h and other adjacent nuclei.

Identification of c-Fos immunoreactive brainstem neurons activated during fictive mastication in the rabbit.

In the present study we used the expression of the c-Fos-like protein as a "functional marker" to map populations of brainstem neurons involved in the generation of mastication. Experiments were conducted on urethane-anesthetized and paralyzed rabbits. In five animals (experimental group), rhythmical bouts of fictive masticatory-like motoneuron activity (cumulative duration 60-130 min) were induced by electrical stimulation of the left cortical "masticatory area" and recorded from the right digastric motoneuron pool. A control group of five animals (non-masticatory) were treated in the same way as the experimental animals with regard to surgical procedures, anesthesia, paralysis, and survival time. To detect the c-Fos-like protein, the animals were perfused, and the brainstems were cryosectioned and processed immunocytochemically. In the experimental group, the number of c-Fos-like immunoreactive neurons increased significantly in several brainstem areas. In rostral and lateral areas, increments occurred bilaterally in the borderzones surrounding the trigeminal motor nucleus (Regio h); the rostrodorsomedial half of the trigeminal main sensory nucleus; subnucleus oralis-gamma of the spinal trigeminal tract; nuclei reticularis parvocellularis pars alpha and nucleus reticularis pontis caudalis (RPc) pars alpha. Further caudally-enhanced labeling occurred bilaterally in nucleus reticularis parvocellularis and nucleus reticularis gigantocellularis (Rgc) including its pars-alpha. Our results provide a detailed anatomical record of neuronal populations that are correlated with the generation of the masticatory motor behavior.

Physiological characterization, localization and synaptic inputs of bursting and nonbursting neurons in the trigeminal principal sensory nucleus of the rat.

A population of neurons in the trigeminal principal sensory nucleus (NVsnpr) fire rhythmically during fictive mastication induced in the in vivo rabbit. To elucidate whether these neurons form part of the central pattern generator (CPG) for mastication, we performed intracellular recordings in brainstem slices taken from young rats. Two cell types were defined, nonbursting (63%) and bursting (37%). In response to membrane depolarization, bursting cells, which dominated in the dorsal part of the NVsnpr, fired an initial burst followed by single spikes or recurring bursts. Non-bursting neurons, scattered throughout the nucleus, fired single action potentials. Microstimulation applied to the trigeminal motor nucleus (NVmt), the reticular border zone surrounding the NVmt, the parvocellular reticular formation or the nucleus reticularis pontis caudalis (NPontc) elicited a postsynaptic potential in 81% of the neurons tested for synaptic inputs. Responses obtained were predominately excitatory and sensitive to glutamatergic antagonists DNQX and/or APV. Some inhibitory and biphasic responses were also evoked. Bicuculline methiodide or strychnine blocked the IPSPs indicating that they were mediated by GABA(A) or glycinergic receptors. About one-third of the stimulations activated both types of neurons antidromically, mostly from the masseteric motoneuron pool of NVmt and dorsal part of NPontc. In conclusion, our new findings show that some neurons in the dorsal NVsnpr display both firing properties and axonal connections which support the hypothesis that they may participate in masticatory pattern generation. Thus, the present data provide an extended basis for further studies on the organization of the masticatory CPG network.

Integration in trigeminal premotor interneurones in the cat. 1. Functional characteristics of neurones in the subnucleus-gamma of the oral nucleus of the spinal trigeminal tract.

The profile of integration in a sample of 183 interneurones localized in the subnucleus-gamma of the oral nucleus of the spinal trigeminal tract (NVspo-gamma) has been analyzed. 134 neurones were tested for inputs from primary afferents of the trigeminal, facial and cervical nerves as well as for inputs from the midbrain and from the cervical spinal cord. The remaining 49 neurones were tested for inputs from the primary afferents and for descending convergence from defined sites within the oro-facial primary projections of the cerebral cortex. It was found that the interneurones, mainly recorded in the dorsal and dorsomedial aspect of the NVspo-gamma, receive short latency inputs from the low threshold oral and perioral afferents and longer latency inputs from the high threshold jaw and neck muscle afferents. There was evidence for convergence from the cervical segmental level (29%) and some of the neurones had axon terminals in the superior colliculus. However, the interneurones did not receive a descending tectal input. About 80% of the NVspo-gamma interneurones were activated from the orofacial primary projection fields within cytoarchitectonic areas 3a and 3b of the coronal gyrus. This input was topographically organized and the neurones were activated from the same oral and perioral region of the periphery as the cortical region from which the descending projections themselves originated. Minimum latencies indicated a monosynaptic connection. The convergence profile onto the NVspo-gamma interneurones appeared unique as compared with interneurones located in the intertrigeminal area. Aspects of the possible functional roles of the NVspo-gamma neurones are discussed in relation to ongoing oro-facial ("masticatory") movements. The properties of a selected sample of NVspo-gamma interneurones, which were antidromically activated from the digastric subnucleus of the trigeminal motor nucleus, are reported in a companion paper (Olsson and Westberg 1991).

Integration in trigeminal premotor interneurones in the cat. 2. Functional characteristics of neurones in the subnucleus-gamma of the oral nucleus of the spinal trigeminal tract with a projection to the digastric motoneurone subnucleus.

Seventy-one (n = 71) premotor interneurones have been localized by extracellular recordings within the subnucleus-gamma of the oral nucleus of the spinal trigeminal tract (NVspo-gamma) in nineteen chloralose anaesthetized cats. The neurons were antidromically activated by microstimulation (minimum = 3 microA) applied to the digastric motoneurone subnucleus of the trigeminal motor nucleus. Fifty-one (n = 51) of the interneurones were discharged from the ipsi- and nineteen (n = 19) from the contralateral digastric subnucleus. One neurone out of four tested was antidromically activated from both stimulation sites suggesting a bifurcated axon. The identified premotor neurones had a unique convergence profile of oral and perioral primary afferents. Latency calculations indicated that at least 55% of these interneurones were monosynaptically activated by low stimulus strength applied to the inferior alveolar (minimum = 1.0 T) and/or the lingual nerve (minimum = 1.0 T). The thresholds for evoking the neuronal discharges coincided statistically with those required to evoke a jaw opening reflex response by stimulation of the same nerves. It is suggested that the specific group of NVspo-gamma interneurones under different contexts mediates the disynaptic reflex and participates in the centrally and reflexly evoked "patterning" adjustments of the digastric jaw opening motoneurones during ongoing jaw movements. A companion paper reports the convergence of descending cortical, tectal and ascending cervical inputs, as well as of oro-facial and neck primary afferent inputs onto an unselected population of interneurones in the NVspo-gamma (Westberg and Olsson 1991).

Evidence that trigeminal brainstem interneurons form subpopulations to produce different forms of mastication in the rabbit.

To determine how trigeminal brainstem interneurons pattern different forms of rhythmical jaw movements, four types of motor patterns were induced by electrical stimulation within the cortical masticatory areas of rabbits. After these were recorded, animals were paralyzed and fictive motor output was recorded with an extracellular microelectrode in the trigeminal motor nucleus. A second electrode was used to record from interneurons within the lateral part of the parvocellular reticular formation (Rpc-alpha, n = 28) and gamma- subnucleus of the oral nucleus of the spinal trigeminal tract (NVspo-gamma, n = 68). Both of these areas contain many interneurons projecting to the trigeminal motor nucleus. The basic characteristics of the four movement types evoked before paralysis were similar to those seen after the neuromuscular blockade, although cycle duration was significantly decreased for all patterns. Interneurons showed three types of firing pattern: 54% were inactive, 42% were rhythmically active, and 4% had a tonic firing pattern. Neurons within the first two categories were intermingled in Rpc-alpha and NVspo-gamma: 48% of rhythmic neurons were active during one movement type, 35% were active during two, and 13% were active during three or four patterns. Most units fired during either the middle of the masseter burst or interburst phases during fictive movements evoked from the left caudal cortex. In contrast, there were no tendencies toward a preferred coupling of interneuron activity to any particular phase of the cycle during stimulation of other cortical sites. It was concluded that the premotoneurons that form the final commands to trigeminal motoneurons are organized into subpopulations according to movement pattern.

Integration in trigeminal premotor interneurones in the cat. 3. Input characteristics and synaptic actions of neurones in subnucleus-gamma of the oral nucleus of the spinal trigeminal tract with a projection to the masseteric motoneurone subnucleus.

A population of last-order interneurones within the rostrodorsal part of the oral nucleus of the spinal trigeminal tract (NVspo-gamma) has been investigated in 21 chloralose anaesthetised cats. The neurones were identified by their antidromic (AD) response to microstimulation (median current 9 microA, range 3-39 microA) of the ipsior the contralateral masseteric subnucleus of the trigeminal motor nucleus. Fifty-one of 113 interneurones tested were discharged from the ipsilateral and eight from the contralateral motor nucleus. The average conduction time was 0.50 ms from the ipsilateral and 0.74 ms from the contralateral motoneurone pool. Conduction velocities of the axons ranged from 2.0 to 14.0 ms. The pattern of primary afferent input onto the selected neurones was analysed by graded electrical stimulation of dissected trigeminal nerves. Low-threshold afferents innervating the intraoral mucosa including the tongue and the perioral skin of the lower lip were the most effective inputs, as judged from both the frequency of occurrence and from the latencies of the evoked spike discharges. Ninety-six percent of the neurones responded to stimulation of the inferior alveolar nerve (Alv inf) and 83% responded to stimulation of the lingual nerve (Ling). The median threshold strength required to evoke the Alv inf and the Ling responses was 1.7 T (range 1.0-3.6 T) and 1.3 T (range 1.0-5.0 T), respectively. The median latency to spike discharges evoked by the Alv inf was 2.0 ms (range 1.3-4.8 ms) and to the Ling it was 2.5 ms (range 1.4-7.0 ms). Action potentials elicited by stimulation of the masseteric and digastric nerves were observed in 40% and 10% of the neurones, respectively. These responses, which had median latencies of more than 8 ms (range 4.7-16.0 ms), were only seen at stimulation intensities above 2 T (range 2.5-25 T). An input from the maxillary whisker nerve was seen in only one case. Postspike averages of the extracellular field potentials within the trigeminal motoneurone subnuclei evoked by interneuronal spikes were made in a subsample of 51 NVspo-gamma neurones activated by iontophoresis of L-glutamic acid. Excitatory synaptic effects within the masseteric subnucleus were observed in eight cases. An inhibitory effect was seen in one case. One specific neurone gave an excitatory extracellular field potential within the digastric motoneurone subnucleus. This interneurone was AD activated from the digastric, but not from the masseteric subnucleus.(ABSTRACT TRUNCATED AT 400 WORDS)

Location of, and peripheral convergence on, the interneuron in the disynaptic path from the coronal gyrus of the cerebral cortex to the trigeminal motoneurons in the cat.

Primary afferent and descending cortico-bulbar convergence on 186 interneurons located in the intertrigeminal area was investigated. The experiments were performed on cats anaesthetized with chloralose. Nerves from the three trigeminal dermatomes were stimulated electrically at intensities below and above twice the threshold level. Nerves from oral, perioral and periorbital structures, and afferents from the masseteric and digastric muscles were included. The surface of the cerebral cortex was stimulated electrically in systematically selected, maximally receptive points within the trigeminal primary projection fields. The intertrigeminal neurons generally responded to stimulation of low-threshold afferents from periodontal, lingual or perioral cutaneous receptors with a polysynaptic latency. Inputs from 3-5 nerves were common but one afferent input was usually most effective. The neurons were generally discharged from two or more cortical points, as a rule those of the oral and perioral projection fields in areas 3a and 3b of the coronal gyrus. The fastest path from the cerebral cortex to the intertrigeminal area was monosynaptic. However, the median latency was 4-5 ms which indicates an oligosynaptic path. The path went through the pyramid at the pontine level. The discharge pattern of the intertrigeminal neurons was 1-4 spikes in 54% of the neurons and a high frequency train of spikes in 46%. Cortical excitation followed by inhibition of the neurons was observed. The neurons were not discharged by electrical stimulation in the defence-attack area of the hypothalamus. Transsynaptic responses evoked from the mesencephalon were seen in 1/3 of the tested neurons.

Bulbar neurones with axonal projections to the trigeminal motor nucleus in the cat.

The location of bulbar neurones with axons projecting to the ipsi- and contralateral trigeminal motor nucleus were investigated in cats anaesthetized with sodium pentobarbital. Wheat germ agglutinin-conjugated horseradish peroxidase (WGA-HRP) was injected in amounts of 5-24 nl. A volume-calibrated microelectrode was used for recording of evoked potentials and pressure injection of WGA-HRP. The injection site was guided by the position where a maximal antidromic response was evoked by electrical stimulation of the masseteric nerve. The survival time was 19-22 h. In preparations with the depot located in the masseteric subnucleus retrogradely stained neurones were found bilaterally in the borderzone of the trigeminal motor nucleus. Dense populations of stained neurones were observed ipsi- and contralaterally in the dorsal division of the main sensory trigeminal nucleus and the subnucleus-gamma of the oral nucleus of the spinal trigeminal tract. Clusters of WGA-HRP-neurones were observed bilaterally in the lateral tegmental field at the level of the subnucleus-beta of the oral nucleus of the spinal trigeminal tract, bilaterally dorsal to the facial nucleus and contralaterally adjacent to the hypoglossal nucleus. No stained neurones were found in the gigantocellular reticular nucleus. A group of stained neurones was located in the marginal nucleus of brachium conjunctivum and some were found in the raphé nuclei near obex. Cell profiles were of two types: medium-sized neurones with a triangular profile and 30-40 micron diameter, and fusiform neurones 10 X 50-70 micron. Convergence of descending cortical and trigeminal afferent inputs on interneurones located in the lateral borderzone of the trigeminal motor nucleus, i.e. the intertrigeminal area, is reported in the preceding paper.

Informed consent in clinical training--patient experiences and motives for participating.

The purpose of this study was to assess patients' attitudes to and experiences of participating in the clinical training of medical students. Samples of patients (n = 582) selected at random from six different departments (gynaecology, psychiatry, internal medicine, paediatrics, urology and a health care centre with general practitioners) were interviewed by means of a questionnaire. The patients were selected from those who had consulted the actual departments in the last six months of 1995. Four hundred and forty-one patients (76%) answered the questionnaire. Seventy-one per cent of all patients had experience of participating; of these 41% had estimated that they had once or several times participated without being informed. Eighty per cent felt aggrieved if they were not informed. On average 88% were, in principle, positive to participating. Of those who were, in principle, negative a majority had negative experiences of participating. Elderly patients tended to accept participating more often without being informed. Almost all patients seemed to be positive to participating in the education of medical students, although a silent precondition might be that patients should be informed and given the opportunity to abstain.