Spatiotemporal analysis of spontaneous myogenic contractions in the urinary bladder of the rabbit: timing and patterns reflect reported electrophysiology.

The dynamics of propagating myogenic contractions in the wall of the resting ex vivo urinary bladder of the rabbit were characterized by spatiotemporal maps and related to cyclic variation in intravesical pressure (Pves). Patches of propagating contractions (PPCs) enlarged and involuted in near synchrony with peaks in Pves [mean 3.85 ± 0.3 cycles per minute (cpm)] and were preceded by regions of stretch. The maximum area of the bladder undergoing contraction (55.28 ± 2.65%) and the sizes of individual PPCs (42.61 ± 1.65 mm2) coincided with the peak in Pves PPCs originated and propagated within temporary patch domains (TPDs) and comprised groups of nearly synchronous cyclic propagating individual contractions (PICs). The TPDs were located principally along the vertical axis of the anterior surface of the bladder. The sites of origin of PICs within PPCs were inconsistent, consecutive contractions often propagating in opposite directions along linear maps of strain rate. Similar patterns of movement occurred in areas of the anterior bladder wall that had been stripped of mucosa. Pves varied cyclically with area of contraction and with the indices of aggregation of PPCs, indicating that they grew by peripheral enlargement and collision without annihilation. The synchronization of PICs within PPCs was sometimes lost, uncoordinated PICs then occurring irregularly (between 4 and 20 cpm) having little effect on Pves We postulate that the formation and involution of PPCs within a TPD resulted from cyclic variation in excitation that increased the incidence and distance over which component PICs propagated.

Advanced spatiotemporal mapping methods give new insights into the coordination of contractile activity in the stomach of the rat.

We used spatiotemporal mapping of strain rate to determine the direction of propagation and amplitudes of the longitudinal and circumferential components of antrocorporal (AC) contractions and fundal contractions in the rat stomach maintained ex vivo and containing a volume of fluid that was within its normal functional capacity. In the region of the greater curvature the longitudinal and circular components of AC contractions propagated synchronously at right angles to the arciform geometric axis of the stomach. However, the configuration of AC contractions was U shaped, neither the circular nor the longitudinal component of contractions being evident in the upper proximal corpus. Similarly, in the distal upper antrum of some preparations, circumferential components propagated more rapidly than longitudinal components. Ongoing "high-frequency, low-amplitude myogenic contractions" were identified in the upper proximal gastric corpus and on the anterior and posterior wall of the fundus. The amplitudes of these contractions were modulated in the occluded stomach by low-frequency pressure waves that occurred spontaneously. Hence the characteristics of phasic contractions vary regionally in the antrum and corpus and a previously undescribed high-frequency contractile component was identified in the proximal corpus and fundus, the latter being modulated in synchrony with cyclic variation in intrafundal pressure in the occluded fundus.

The effect of increasing the nutrient and amino acid concentration of milk diets on dairy heifer individual feed intake, growth, development, and lactation performance.

Increasing early (<3 mo) nutrient feeding levels and growth rate of dairy calves has been found to increase their milk production potential. The objective of this study was to compare the effect of offering milk diets with or without added carbohydrates and amino acids on calf growth, weaning age, and subsequent growth and milk yield of dairy heifers in their first lactation. Friesian calves born at Massey University (n=57) were selected at random, weighed, and allocated to receive 1 of 3 diets. All calves were fed colostrum from 1 to 3d of age, followed by 4 L of whole milk (WM) per head per day and probiotics between 3 and 18d of age. At 18d of age, calves were weighed to ensure mean body weight (BW); then, at 19 d of age, calves changed diets to 1 of 3 treatments, which reached full treatment rate at 21 d of age. The diets were 4 L/head per day of WM (M); 4 L/head per day of WM plus 200 g of plant carbohydrates (MP); and 4 L/head per day of WM plus 200 g of plant carbohydrates with amino acids (MPA). Calves were weaned upon reaching a BW of 90 kg. During this period, BW, body condition, and hip height and width were measured. The heifers were commingled and grazed on ryegrass and white clover pastures until calving at 23 mo of age, when BW, body condition, and hip height and width were measured again. Milk yield and composition were measured throughout first lactation. At weaning, calves fed MPA had greater mean BW gain, a lower number of days to target BW, and a greater mean hip width gain compared with calves in the M group, although mean gain in hip height did not differ among treatments. Total calf starter intake during the milk period was lower for MPA-fed calves compared with those offered M, mainly due to a shorter milk feeding period required to attain the 90-kg weaning weight, whereas mean daily starter intake and straw intake did not differ. No difference was observed in the calving rate or calving age of heifers in any of the dietary feeding groups. First lactation fat-corrected milk yield, milk fat percentage, and total milk fat and protein yields were greater for animals reared on MP and MPA compared with M. Body weight, hip height and width at parturition, milk protein percentage, somatic cell count, or days in milk did not differ among treatments. Increasing nutrient intake, during the milk feeding period, improved the BW gain of calves and milk production of dairy heifers during first lactation.

Potent contact allergen in the rubber plant guayule (Parthenium argentatum).

Chemical and dermatotoxicological investigations of the natural and processed resin of the Mexican rubber plant, guayule (Parthenium argentatum), has established the presence of a sesquiterpene cinnamic acid ester (guayulin A) that is a potent elicitor of allergic contact dermatitis in experimental animals. The guayule contact allergen is comparable to the poison ivy skin allergens as an elicitor of dermatitis in sensitized guinea pigs.

Pathophysiology in Teladorsagia (Ostertagia) circumcincta-infected sheep selected for high fleece weight.

Resilience to parasitism is considered to be the maintenance of growth and production during infection, probably associated with an immune response with lesser detrimental effects on the host relative to adverse effects on the parasite. Resilience to infection with Teladorsagia circumcincta was investigated in lambs from a flock selected for forty generations for high fleece weight (HFW), but with higher FEC and worm burdens than their unselected control (C) flock run in parallel. After recovery from surgery to implant abomasal cannulae, four parasite-naïve lambs from each flock were infected intraruminally at 6.5 months-of-age with 50,000 T. circumcincta L3, then from Day 35 to 70 post infection with 10,000 larvae at weekly intervals. Blood, abomasal fluid and faecal samples were collected daily to Day 35 and thence twice weekly for measurement of serum gastrin and pepsinogen concentrations, blood eosinophils, abomasal pH and FEC. Abomasal worm counts were made after necropsy on Day 94. Skin biopsies were collected weekly for estimation of the percentage of wool follicles containing paracortical cells. Total serum immunoglobulin and IgG1, IgG2, IgA and IgM titres specific for T. circumcincta antigens were estimated twice weekly to Day 42 p.i., then weekly. After the primary challenge, FEC were higher in the HFW lambs, whereas neither group shed many eggs during the 5-week trickle infection; worm burdens were small at post mortem. Resilient HFW lambs showed a lesser inflammatory response, but relatively small differences in abomasal secretion. Circulating eosinophil counts increased moderately in both groups, less in the HFW lambs, during the primary infection and more markedly during the subsequent trickle infection, when the increase in the C lambs became significantly greater. All measured serum antibody titres were low in both groups throughout. Selection for HFW altered the wool characteristics of parasite-naïve lambs (fewer follicles containing paracortical cells). There was a slower increase in the percentage of follicles containing these cells after primary infection. Abomasal function was similar in the two groups, both exhibiting typical increases in abomasal pH and serum gastrin and pepsinogen concentrations. The most marked differences in the HFW lambs were a greater rise in serum pepsinogen during the primary infection and the 2-day delay in onset of hypoacidity. Resilience to parasitism in this flock is consistent with maintenance of wool quality and small differences in abomasal secretion resulting from an attenuated immune response causing fewer detrimental effects on host tissues.

Continuous wavelet analysis of postprandial EGGs suggests sustained gastric slow waves may be slow to develop in infants with colic.

BACKGROUND: Electrogastrography in conjunction with Fast Fourier transform has limited success in detecting low grade abnormalities in gastric electrophysiological activity owing to the non-stationarity of the signal. Analysis by continuous wavelet transform is suitable for non-stationary signals and was used to analyse EGG activity in babies with and without colic. METHODS: Thirty minute postprandial EGG recordings were obtained from 23 sleeping breast-fed infants with clinically validated recurrent colic and 26 breast-fed non-colicky infants. Continuous wavelet transform analysis (CWT) identified three principal frequency components. The mean, standard deviation, and the number of frequency maxima that fell below one standard deviation from the mean were determined for each infant and each frequency. KEY RESULTS: Three component frequencies in the ranges 1.4-2.5 cpm, 2.5-4.0 cpm, and 4.0-15 cpm were found in all EGGs. Pairwise comparisons of the characteristics of each of the frequency ranges by univariate analyses showed significant differences between colicky and non-colicky subjects only in the number of maxima in the mid range of frequencies that lay below one standard deviation from the mean. However, CWT based on all frequencies allowed discrimination of the EGGS of colicky from non-colicky babies on a basis of number of frequency maxima below one standard deviation from the mean in the midrange of frequencies and in the mean and standard deviation in the low range of frequencies that was likely a harmonic of the midrange. CONCLUSIONS & INFERENCES: CWT allowed distinction of EGG signals from colicky and healthy babies. The results indicate that colic may result from tardiness in the establishment of coherent propagation of the gastric slow wave in colicky babies.

Vagal and splanchnic afferent nerves are not essential for anorexia associated with abomasal parasitism in sheep.

Heavy burdens of the abomasal nematode, Ostertagia (Telodorsagia) circumcincta, in growing lambs result in a reduction in liveweight gain due largely to a drop in voluntary feed intake. The present study investigated: (1) the role of subdiaphragmatic vagal and non-vagal visceral afferent nerves in mediating a reduction in voluntary feed intake, using subdiaphragmatic vagal deafferentation (vagotomy) either alone or in combination with coeliac-superior mesenteric ganglionectomy (vagotomy and sympathectomy); and (2) the association between appetite, abomasal pH, selected blood values (amidated gastrin (G-17-amide), glycine-extended gastrin (G-17-Gly), pepsinogen and leptin) and worm burden, in sheep experimentally infected with 100,000 O. circumcincta infective larvae per os. Neither vagotomy alone nor vagotomy and sympathectomy in combination adversely affected the establishment or course of development of the parasite burden, when compared with a control group subject to sham surgery. Furthermore, neither surgical procedure prevented the drop in appetite seen 5-10 days post-infection, although combined vagotomy and sympathectomy did reduce voluntary feed intake prior to the start of the study. Ostertagia infection resulted in a significant increase in abomasal pH in all three groups, which was accompanied by an increase in blood G-17-amide and in G-17-Gly, the latter reported for the first time in parasitized ruminants. There were no significant differences in blood leptin, also reported for the first time in parasitized sheep, either between groups or in comparison with pre-infection levels, though weak negative correlations were established between blood leptin and appetite from day 5 to the end of the study in all three groups and a positive correlation with blood G-17-amide in the control group over the same period. These data suggest that neither intact subdiaphragmatic vagal afferent nerves or coeliac-superior mesenteric ganglion fibres, nor changes in circulating gastrin and leptin concentrations play a major role in mediating the hypophagic effects of O. circumcincta in parasitized sheep.

Sympathetic (alpha-beta) or calcium channel blockade for hypertensive myocardial infarction? A haemodynamic comparison of labetalol and nifedipine.

The haemodynamic impact of alpha- and beta-adrenoceptor blockade (labetalol) was compared with that of slow-calcium channel blockade (nifedipine) in 32 patients with sustained elevation of systemic arterial pressure (systolic blood pressure greater than 160; diastolic blood pressure greater than 95 mmHg) following a recent myocardial infarction (6-22 h). Patients with normal (pulmonary artery occluded pressure; (PAOP less than 18 mmHg; n = 16) or impaired (PAOP greater than 18 mmHg; n = 16) left ventricular function were randomized to labetalol (1 mg/kg i.v. 15 min) or nifedipine (20 mg sublingually) and haemodynamic profile was measured over 2 h. Both drugs equally reduced mean systemic arterial pressure (P less than 0.01 versus pretreatment control), and presumably left ventricular afterload; however, the heart rate (P less than 0.01) and cardiac index (P less than 0.01) increased after nifedipine, contrasting with reductions in both variables following labetalol (P less than 0.01). The elevated left ventricular filling pressure was reduced by both labetalol (P less than 0.05) and nifedipine (P less than 0.01) but the reduction was greater following nifedipine (-2 mmHg versus -5 mmHg, P less than 0.05). Thus both compounds were equally effective hypotensive agents. Labetalol consistently reduced cardiac stroke work and double product, important determinants of myocardial oxygen requirements; however, nifedipine afforded some improvement in cardiac performance in patients with left ventricular dysfunction.

Effects of adult and larval Haemonchus contortus on abomasal secretion.

Abomasal pH and serum pepsinogen and gastrin were increased in parasite-naive sheep by infection with either larval or adult H. contortus. Four sheep received 10000 larvae intraruminally and 9000 adult worms were given directly via an abomasal cannula to another 4 sheep. The latter animals were dosed orally with 0.4 mg kg-1 ivermectin 4 days after worm transfer and their recovery was monitored for a further 8 days. Whereas the presence of adult worms rapidly induced changes in the secretory activity of the abomasum, the early larval stages had minimal effects up to the 4th day post-infection. After either larval or adult infection, the initial hypergastrinaemia began at the same time as the increase in abomasal pH, but serum gastrin continued to increase after abomasal pH had reached a maximum and returned more slowly to normal values after drenching. The increase in serum pepsinogen did not precede those in the other parameters, unlike the earlier hyperpepsinogenaemia which occurs with Ostertagia infection. Three of the 8 infected sheep had no detectable serum pepsinogen increase during the parasitism while showing typical effects on abomasal pH and serum gastrin. The rapidity of the responses to the transfer of adult worms and to their removal by treatment with anthelmintic supports a role for worm excretory/secretory (ES) products which possibly are not produced by the early larval stages. The similarity of responses to H. contortus and O. circumcincta infection suggests the involvement of the same or very similar ES products.

Infection of sheep with adult and larval Ostertagia circumcincta: effects on abomasal pH and serum gastrin and pepsinogen.

Infection of sheep with adult or larval O. circumcincta increased serum pepsinogen and gastrin and abomasal pH. The upper limits of the normal range, calculated from over 1000 samples collected from parasite-naive sheep, were set at 2 standard deviations above the mean; these were for serum pepsinogen, 454 mU tyrosine l-1; serum gastrin, 64 pM and abomasal pH, 3.26. Five infection regimes were used: sheep previously exposed to field parasitism were infected with 30,000 larvae intraruminally (Group A), while parasite-naive sheep were administered either 50,000 larvae intraruminally (Group B), 150,000 larvae intraruminally followed by a trickle infection of 10,000 larvae thrice weekly from days 21 to 45 (Group C), 150,000 exsheathed larvae via an abomasal cannula (Group D) or 15,000 adult worms via an abomasal cannula (Group E). Whereas the presence of adult worms rapidly increased serum pepsinogen (after 8 h) and abomasal pH and serum gastrin (after about 19 h), the early infective larval stages, regardless of the infection regime, had minimal effects until the abrupt rise in all parameters 5-6 days after infection. Abomasal pH returned to near normal levels when the infections became patent and was not re-elevated by a subsequent trickle infection, whereas serum gastrin and pepsinogen remained high. The initial hypergastrinaemia was coincident with the increased abomasal pH, but was preceded by the increase in serum pepsinogen. In several sheep, serum pepsinogen increased very little during the parasitism, although there were typical effects on abomasal pH and serum gastrin. Serum gastrin was depressed when the abomasal pH exceeded about 5.5. It is suggested that an inhibitor of gastrin release is generated by proliferating abomasal microbes under these conditions and that this is a limitation to the use of elevated serum gastrin in the diagnosis of parasitism in individual sheep.

Infection of sheep with adult and larval Ostertagia circumcincta: gastrin.

Gastric endocrine cell populations and serum and tissue gastrin have been examined in sheep which were infected either intraruminally by tube with 150,000 Ostertagia circumcincta larvae followed by a trickle infection of 10,000 larvae thrice weekly for 8 weeks or by the transfer of 15,000 adult worms directly into the abomasum and killed 8 days later. Depletion of both antral gastrin and somatostatin was evident in both groups: tissue gastrin concentrations were reduced by 85% in the trickle infection and both G cells (gastrin-containing) and D cells (somatostatin-containing) were pale and fewer after adult worm transfer. The concurrent depletion of antral gastrin and somatostatin supports the contention that the hypergastrinaemia in parasitised sheep is largely secondary to the increase in abomasal pH. Although there was no change in the proportions of G34 and G17 in the tissues, there was an increase in the longer form of gastrin in the circulation of the larval-infected sheep, suggesting that there may be differential secretion of G17 and G34 which may be exaggerated as the rate of secretion increases. Although the fundic mucosa was thicker following trickle infection, there was no evidence of enterochromaffin-like cell hyperplasia in either infected group. It is suggested that hyper-gastrinaemia may be beneficial to the host, as it may allow the abomasum to regain the ability to acidify its contents during continued exposure to the parasites.

Infection of sheep with adult and larval Ostertagia circumcincta: abomasal morphology.

The infection of parasite-naive sheep with approximately 15,000 adult Ostertagia circumcincta via abomasal cannulae resulted in marked changes in the structure and function of the abomasum. The functional changes, which have been characterised previously, included elevated abomasal pH and increased serum concentrations of pepsinogen and gastrin. Eight days after the transplant of adult worms, the abomasa of recipient animals were significantly heavier than those of controls (P < 0.001), the thickness of the fundic mucosa was greater (P < 0.01), there were fewer parietal cells (P < 0.01) and increases in the numbers of mitotic figures and mucus-producing cells. Mucous cell hyperplasia was also evident in the fundic mucosae of sheep receiving a trickle infection of infective, third-stage O. circumcincta larvae and was prominent within nodules associated with larval development. In non-nodular mucosa, there was hyperplasia of mucous cells and changes in the distribution of parietal cells. Decreases in the number of parietal cells at the gland base were offset by increases at a mid-gland level, probably due to chronic hypergastrinaemia, so that, overall, total parietal cell number was unaffected. Mucous cell hyperplasia and the diminution of parietal cell number are seen in a diverse range of disease states and may be mediated by host growth factors such as Transforming growth factor-alpha. Alternatively, the cellular and/or the secretory changes in response to the presence of adult worms are mediated by chemicals that are cytotoxic/inhibitory for parietal cells, and released by the parasites themselves.

Sesquiterpene lactone dermatitis. Cross-sensitivity in costus-sensitized patients.

Thirteen costus-sensitive patients were patch tested with 38 sesquiterpene lactones of five different classes over a two-year period. Cross-reacting agents fell into two chemical categories: (1) those that resembled the primary sensitizer, and (2) those belonging to different skeletal classes. An exocyclic methylene group conjugated to a gamma-lactone was present in both chemicals that cross-reacted and those that did not. The difference between these two groups is that cross-reacting chemicals are not highly substituted, tending to be lipophilic, while those giving negative responses all are highly substituted at the C-8/C-6 position. This functional group may hinder binding of exocyclic methylene with skin protein or the actual antigenic site with an immune receptor cell.

Morphological changes in the oesophagus of newborn pigs: effects of age, diet and oral insulin-like growth factor I (IGF-I) or IGF-II.

It has been reported in the literature that the stomach and the intestine in newborns undergo profound growth and functional maturation during the immediate postnatal period and diet ingestion has a significant impact on these changes. The present paper examines oesophageal development in newborn pigs during the first three postnatal days and the effects of diet and oral insulin-like growth factor I (IGF-I) or IGF-II on oesophageal morphology. It was observed that marked changes, including reduction in thickness of the epithelium, accelerated proliferation and migration of basal epithelial cells and increased accumulation of mucus in the glandular cells, occurred during the first postnatal day following onset of natural suckling. Bottle-feeding with various liquid diets (i.e. porcine colostrum, bovine colostrum, bovine milk, and infant milk formula), induced marked morphological changes which were similar to those induced by natural suckling. However, bottle-feeding with water did not result in marked reduction in the thickness of the epithelium nor did it accelerate basal epithelial cell proliferation and migration. Oral IGF-I, but not IGF-II, increased basal epithelial cell proliferation up to 81%. Owing to a large inter-animal variation, the increment did not reach a significant level (P = 0.071). The results suggest that chemical constituents in the diet and physical stimulation of food ingestion, which cause sloughing off of luminal surface tissue, are two major stimuli or epithelial cell proliferation in the new born oesophagus.

A sequential study of the pathology associated with the infection of sheep with adult and larval Ostertagia circumcincta.

Disturbances in the physiology of the abomasa of sheep infected with either adult Ostertagia circumcincta given via abomasal cannulae, or larvae (L3) given intraruminally were matched by pathological changes in tissues collected by repeated mucosal biopsy. Within 2-3 days of the transplant of adult worms, abomasal pH had increased markedly in five out of six animals, and there also had been rapid increases in serum gastrin and pepsinogen concentrations in all animals. Reductions in parietal cell number were recorded as early as 1 day after the transplant of adults and were associated with the rapid accumulation of many neutrophils and eosinophils. Mucosal hyperplasia, with increased numbers of cells closer in appearance to mucous/mucous neck cells, was a relatively late development, being most pronounced in the latter part of the infection. In sheep given larvae, changes in secretory physiology were again matched by a concurrent fall in parietal cell number and by the accumulation of inflammatory cells. Changes became maximal when most worms could be expected to be present as adults, confirming the role of adults in the natural disease. Some abnormalities were detected in biopsies collected from animals maintained free of parasites and, although milder in degree, there were similarities to those observed in parasitised tissues, there being fewer parietal cells, a modest degree of mucous cell hyperplasia and inflammatory infiltrates of predominantly neutrophils. These changes were the likely result of trauma to the tissues in the immediate vicinity of the cannula, due either to the presence of the cannula itself or to the frequent collection of biopsy material from areas close to it.

Circulatory effects of intravenous and oral atenolol in acute myocardial infarction.

The hemodynamic dose-response effects of intravenous (0.05 and 0.10 mg/kg) and oral (50 and 100 mg) atenolol were compared in a randomized between-group study of 24 men within seventeen hours of an acute uncomplicated myocardial infarction; 6 subjects were evaluated in each of the four groups. Hemodynamic variables were determined over a one-hour control period, following which the randomized dose of atenolol was administered and measurements repeated at 15 (intravenous therapy only), 30, 60, 90, 120, 180, 240, 300, and 360 minutes. The peak hemodynamic effect was similar and independent of either the dosage or route of administration. In all groups atenolol reduced heart rate and cardiac and stroke volume indices. The pulmonary artery occluded pressure and systemic vascular resistance index were transiently increased. Mean arterial pressure was significantly reduced only in the oral group with the highest pretreatment pressure. Maximum changes developed between fifteen and thirty minutes after intravenous dosing and between two and three hours after oral dosing. However, substantial reductions in cardiac index (-0.6 L/min/m2; p less than 0.05) were already achieved at sixty minutes following oral dosing. The duration of pharmacodynamic activity was for two to three hours following intravenous and for the study duration (four to six hours) after oral dosing. These data confirm the hemodynamic safety of atenolol after acute myocardial infarction.

Immunoreactive gastrin concentrations in gastrointestinal tissues of sheep.

Radioimmunoassay of gastrin in gastrointestinal tissues of lambs and adult sheep showed highest concentrations (796 to 11,156 pmol g-1 mucosa) in the antral region of the abomasum. The next highest concentrations of gastrin were in the proximal duodenal mucosa (16 to 518 pmol g-1). Gastrin was undetectable or present in lower concentrations in caudal regions of the duodenum (less than 11 X 5 pmol g-1), the pancreas and in the body of the stomach. It is concluded that the distribution of gastrin secreting cells in sheep is similar to that in other animals.

Changes in plasma pancreatic polypeptide and gastrin in sows after eating and atropine.

Changes in plasma gastrin, pancreatic polypeptide and pulse rate were examined in three adult female pigs in which venous cannulae had been placed and in two of which arterial cannulae allowed sampling of arterial blood or recording of pulse rate. Gastrin, pancreatic polypeptide and pulse rate increased when the pigs ate after fasting overnight. Pancreatic polypeptide was reduced to or below resting levels following administration of atropine (25, 50 or 100 micrograms/kg intravenously) after which gastrin remained at about its previous levels or rose and pulse rates rose. It is concluded that in the pig, as in other species, there is a cholinergic muscarinic (atropine sensitive) mechanism contributing both to postprandial increases of pancreatic polypeptide and of gastrin.

Electrophysiological characteristics of tension receptors in the abomasal antrum of sheep.

Unitary impulse activity from tension receptors in the abomasal antrum in sheep anaesthetized with chloralose was studied with concurrent measurements of isometric tension in the antral wall, intraluminal pressures and electromyography (EMG). Rhythmical background activity had a close correlation with intraluminal pressure changes and usually a close correlation with local increases in EMG activity and isometric tension. Impulse frequencies increased, but were not sustained, following changes from isotonic to isometric conditions. Tension receptors were excited by transmural compression, by antral distension and by local intra-arterial injections of acetylcholine (2.5-25 micrograms), pentagastrin (10-20 micrograms), 5-hydroxytryptamine (1-20 micrograms), adrenaline (10 micrograms) cholecystokinin-8 (1-5 micrograms) or bradykinin (0.5-20 micrograms), and by systemic injections of bethanecol (5-1000 micrograms). Local intra-arterial perfusions of atropine (50 micrograms) and hexamethonium (100 micrograms) did not abolish spontaneous antral movements or affect the enhanced impulse activity evoked by acetylcholine or 5-hydroxytryptamine. Most antral tension receptors were excited by increases in antral tension or passive distension; they therefore functioned 'in series' with the muscularis externa. The discharges of three tension receptors were 'off-loaded' early during the contraction evoked by local injections of pentagastrin (10-20 micrograms).

Spatiotemporal organization of standing postprandial contractions in the distal ileum of the anesthetized pig.

BACKGROUND: Spatiotemporal (ST) mapping has mainly been applied to ex vivo preparations of the gut. We report the results of ST mapping of the spontaneous and remifentanil-induced motility of circular and longitudinal muscles of the distal ileum in the postprandial anaesthetized pig. METHODS: Spatiotemporal maps of strain rate were derived from image sequences of an exteriorized loop of ileum on a superfusion tray at laparotomy. Parameters were obtained by direct measurement from these maps, and by auto- and cross-correlation of map segments. KEY RESULTS: Localized domains of standing longitudinal and circular activity that alternated between neighboring domains occurred spontaneously and both were promptly extinguished following intraluminal dosage with lidocaine. Longitudinal or circular contractions within a domain typically occurred at times that would coincide with every second or third cycle of the slow wave but propagated within the domain at a rate consistent with that reported within spike patches. Shortly after intravenous administration of remifentanil, longitudinal and circular contractions at the reported slow wave frequency propagated over longer distances at a high speed before slowing to a rate similar to that reported for slow waves. CONCLUSIONS & INFERENCES: ST mapping based on cross-correlation is a robust tool for the analysis of intestinal movement and minimizing movement artefacts. We propose that the ST pattern of standing longitudinal and circular contractions arises from variation in the refractory period of smooth muscle, and hence, in its response to successive slow waves with neural stimuli influencing the former and having a mainly permissive role.