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.

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.

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.

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.

Mucosal microfolds augment mixing at the wall of the distal ileum of the brushtail possum.

BACKGROUND: Recent work suggests that mixing in the small intestine takes place in central luminal and peripheral compartments. However, while movements of villi have been described, the mechanisms by which peripheral mixing are engendered remain unclear. METHODS: We examined the disposition and movement of mucosa and associated villi during contractions of the everted terminal ileum of the brushtail possum. We then simulated the effect of these movements on peripheral mixing. KEY RESULTS: Compression of the intestinal mucosa by phasic longitudinal or radial contractions created short-lived microfolds, which were of similar scale to the attached villi. The packing density of the villous tips increased in the concavities and decreased on the crests of these microfolds. Simulations showed that these caused liquid digesta to be expelled from, or drawn into, intervillous spaces, significantly augmenting peripheral, but not bulk, luminal mixing. CONCLUSIONS & INFERENCES: We describe a mechanism by which peripheral mixing may be engendered by mucosal microfolds without requiring the coordinated contraction of individual villi or groups of villi.

Spatiotemporal mapping of the muscular activity of the gizzard of the chicken (Gallus domesticus).

We report the results of spatiotemporal mapping of the spontaneous actions of component muscles of the gizzard and associated structures in ex vivo preparations with combined superfusion and vascular perfusion. Ongoing spontaneous contraction of cranial and caudal thin muscles occurred at a frequency of 2.2 ± 0.1 cycles per minute. Contractions of M. tenuis craniodorsalis with mean duration of 2.8 ± 0.2 s commenced ventrally adjacent to the distal limit of the proventriculus and progressed dorsally at 2.02 ± 0.03 mm•s(-1) in a concerted front. Near simultaneous contraction of M. tenuis caudoventralis of mean duration of contraction of 4.7 ± 0.7 s commenced dorsally and progressed ventrally at a similar rate (2.1 ± 0.1 mm•s(-1)) and in a similar manner. Contraction of the caudoventralis preceded that of craniodorsalis (mean 1.1 ± 0.15 s). Contraction of the 2 tenuis muscles was synchronous with the first component peak of the cyclic increase in lumen pressure and with distension of the crassus musculature. Contraction of the M. crassus caudodorsalis muscle coincided with the second component peak and was followed by distension of the tenuis musculature. The latter commenced before the relaxation of the tenuis muscles. Contractions of the crassus muscle propagated rapidly at right angles to the orientation of the muscle fibers at a faster velocity than that of the tenuis musculature. The durations of the component peaks in lumen pressure indicated that the duration of crassus contraction was similar to that of the tenuis musculature.

A comparison of the organization of longitudinal and circular contractions during pendular and segmental activity in the duodenum of the rat and guinea pig.

BACKGROUND: Little is known of the spatiotemporal organization of pendular duodenal contractions. METHODS: We used longitudinal and radial spatiotemporal mapping to examine and compare pendular and segmental contractile activity in the proximal duodenum of the rat and guinea pig when the lumen was perfused with saline or micellar decanoic acid. KEY RESULTS: Isolated phasic longitudinal contractions occurred along the rat duodenum with a frequency of 36 ± 2 cpm and strain rate amplitude of 26.8 ± 8.0% s(-1). These contractions occurred at fixed locations along the duodenum forming columns on the longitudinal strain rate map. The strain rate activity had local maxima at 4-6 points spaced at 7.7 ± 4.0 mm intervals along the duodenum and were uncoordinated between neighboring domains. Similarly disposed, less distinct, longitudinal contractions occurred in the guinea pig duodenum at a frequency of 25.2 ± 6.6 cpm with amplitude 6.8 ± 3.6% s(-1) but these were generally accompanied by numerous circular contractions that were distributed over 4-5 fixed locations and occurred with a frequency of 9 ± 3 cpm. Isolated static circular muscle contractions also occurred but at a lower rate in the rat than the guinea pig. Both types of contractions propagated after dosage with tetrodotoxin, lidocaine, atropine, or apamin. CONCLUSIONS & INFERENCES: Localized contractions during segmental and pendular activity had some features of the spike patches that are normally associated with slow wave propagation. However, the commencement of propagation following administration of neural blocking agents and cholinergic inhibitors indicates their localization is maintained by inhibitory elements of the enteric nervous system.

Electroencephalographic responses of halothane - anaesthetised calves to slaughter by ventral-neck incision without prior stunning.

AIM: To investigate whether the electroencephalographic (EEG) responses to slaughter by ventral-neck incision without prior stunning may be perceived as painful in halothane-anaesthetised calves. METHODS: Fourteen Angus steers were minimally anaesthetised with halothane, using an established anaesthesia protocol. EEG indices were recorded bilaterally for 5 minutes prior to and 5 minutes following ventral-neck incision. A single incision was made in the ventral aspect of the neck, severing all tissues ventral to the vertebral column including the major blood vessels supplying and draining the head. Changes in the median frequency (F50), 95% spectral edge frequency (F95) and total power of the EEG (Ptot) were used to investigate the effects of ventral-neck incision. At the completion of the experiment, brains of calves were examined histologically. RESULTS: During the 30 seconds following ventral-neck incision, the F95 and Ptot showed significant changes (p<0.05) compared with pre-treatment values. The F50 increased significantly from recordings from the right side of the cranium. No gross or histological abnormalities were detected in the brains following slaughter. CONCLUSIONS: This study is the first investigation of the noxiousness of slaughter by ventral-neck incision, using EEG spectral analysis. It demonstrated that there is a period following slaughter where ventral-neck incision represents a noxious stimulus.

A quantitative study of the morphological development and bacterial colonisation of the gut of the tammar wallaby Macropus eugenii eugenii and brushtail possum Trichosurus vulpecula during in-pouch development.

We compared the rates of change of various morphological parameters of the stomach, small intestine, caecum and colon of tammar wallabies and brushtail possums with body mass during in-pouch development. These were correlated with changes in the numbers of bacterial species in the various gut segments. In the pouch-young of both species, the wet tissue masses of all gut segments increased with body mass in a positively allometric manner (i.e. with a body mass exponent > 1), suggesting that the mass of each component was disproportionately low at birth, but increased disproportionately rapidly postnatally. However, the lengths of the wallaby stomach and small intestine scaled isometrically with respect to body mass (i.e. with a body mass exponent around 0.33), which may indicate that the shape of these components changes to the adult form during early neonatal development. Conversely, the length of the caecum and colon of both wallabies and possums scaled in a positively allometric manner with respect to body mass, showing area to volume compensation. This may indicate a more general pattern of disproportionately rapid postnatal enlargement in areas that are distal to the principal sites of neonatal digestion (i.e. the stomach). The numbers of bacterial species present in the various gastrointestinal segments of both species were low in animals aged 100 days or less but there was a significant increase in microbial diversity in the caecum of brushtail possums aged over 100 days. The possum caecum also showed the greatest rate of increase in wet tissue mass relative to body mass. It is postulated that caecal development may act as a nidus for establishment of communities of commensal microflora in the developing marsupial.