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PubMedDate not supplied

Electromotor activity of the cecum and ascending colon: the concept of 'individual pacemakers'.

BACKGROUND/AIMS: The cecum is described as differing anatomically from the ascending colon (AC); yet their similarity or difference in terms of motile activity has not been studied sufficiently. The cecum is separated from the AC by the cecocolonic junction (CCJ) which contains a cecocolonic sphincter. We assumed that the motile activity of the AC is different from that of the cecum and hypothesized that both the AC and the cecum might have different pacemakers which initiate the motile activity. This hypothesis was investigated in the current study. METHODS: The study was performed in 10 subjects (mean age 41.6 +/- 12.8 SD years; 7 women) during the repair of huge abdominal incisional hernias. The electric activity was recorded from 2 monopolar electrodes applied each to the cecum, CCJ and AC. The CCJ was then anesthetized by xylocaine and the electric waves of the cecum, CCJ and AC were registered after 10 and 90 min. The test was repeated using normal saline instead of xylocaine. RESULTS: Electric waves were recorded from the cecum, CCJ and AC in the form of monophasic pacesetter (PPs) and action potentials (APs). The PPs occurred regularly and the APs randomly. The frequency, amplitude and conduction velocity of the waves recorded from the CCJ and AC had higher readings than those from the cecum (p < 0.05). The CCJ and AC showed similar frequency and conduction velocity (p > 0.05). Ten minutes after CCJ anesthetization, electric waves were recorded from the cecum but not from the CCJ or AC; however, electric activity returned after 90 min. Saline injection did not affect the electric activity of the cecum, CCJ and AC. CONCLUSION: The electric wave parameters of the cecum differed from those of the CCJ and AC, suggesting that the motile activity of the CCJ and AC is not a continuation of the motile activity of the cecum and that it might be evoked by 2 different pacemakers. The similarity in frequency and conduction velocity of electric waves of the CCJ and AC, however, most likely denotes that the AC waves are a continuation of those of the CCJ, and that both are evoked by the same pacemaker probably located in the CCJ. The higher amplitude of cecal waves might be due to the thicker cecal musculature compared to that of the AC.

Adult↗
PubMed2006

Functional effects and characteristics of cecum-projecting neurons in the dorsal motor nucleus of the vagus of rats.

Preganglionic neurons in the dorsal motor nucleus of the vagus (DMV) innervate most of the gastrointestinal tract; with the stomach and the cecum/proximal colon having a greater proportion of vagal input. Cecum-projecting neurons have been thought to be distinct from other preganglionic neurons due to their location within the DMV, but it is unknown whether these neurons innervate the cecum exclusively or what effect their activation has on cecal motor activity. Therefore, we investigated the extent of coinnervation of cecum and stomach by vagal neurons, their neurochemistry, and the effect of DMV stimulation on intracecal and intragastric volumes. Fluorescent retrograde tracers injected into the serosa of the cecum and stomach revealed that in the DMV 49+/-5% CTB-labeled cecum-projecting neurons also innervated the stomach. Immunocytochemical staining for nitric oxide (NO) synthase and tyrosine hydroxylase indicated that only 3+/-1% and 4+/-1% of cecum-projecting neurons contained these markers, respectively. In anesthetized rats gastric and cecal volumes were measured by prototypic miniaturized dual barostats that were developed for use in rodents. Microinjection of l-glutamate into the DMV increased gastric contractile activity and tone, and reduced on-going cecum contractile activity (2.6+/-0.7 contractions/2 min after injection versus 8.2+/-0.4 contractions/2 min before injection, N = 5). The barostat was able to detect decreases (-0.88+/-0.13 ml) and increases (0.25+/-0.05 ml) in cecum volume in response to carbachol and sodium nitroprusside, respectively. In summary, cecum-projecting neurons are not an entirely exclusive population within the DMV because a percentage of these also innervate the stomach. Central vagal stimulation can modulate both gastric and cecum contractile activity. Together, these data support a role of the vagus in neural reflexes involving gastric and large bowel motor function, such as the immediate phase of the gastrocolonic reflex.

Animals↗
PubMed1998

Disaccharidase activity in rat cecum and colon with hyperplasia induced by maltitol or glucomannan.

The existence of disaccharidases and an enzyme that hydrolyzes maltitol were investigated in the large intestine of rats. In addition, the properties of disaccharidases were studied in the cecum and colon with hyperplasia induced by the ingestion of nondigestible carbohydrates such as maltitol and glucomannan. Maltase activity was detected in the cecal and colonic mucosa of rats fed a regular diet, although it was a very low level as compared with that in the small intestinal mucosa. Maltitol hydrolysis was notably lower in the cecum and colon than in the small intestine. The Km of maltose was 5.56 mM in the small intestine and 5.59 mM in the cecum, while that in the colon was 2.56 mM. The Vmax of maltose was at very low levels in the cecum (0.38 mumol/mg protein/h) and colon (0.37 mumol/mg protein/h) in comparison with that in the small intestine (30.3 mumol/mg protein/h). With regard to the maltitol hydrolyzing enzyme, Km and Vmax were 2.00 mM and 2.51 mumol/mg protein/h in the small intestine, respectively. Km and Vmax in the cecum and colon could not be measured because the level was too low. The tissue weights of the cecum and colon increased significantly in both the maltitol (p < 0.01, p < 0.05) and glucomannan (p < 0.01, p < 0.05) groups in comparison with that of the control group. The specific activity of maltase decreased significantly in the small intestine of the maltitol (p < 0.05) and glucomannan (p < 0.01) groups. However, maltase activity in the cecum and colon was not lowered by maltitol ingestion, although it decreased significantly in the cecum of the glucomannan group (p < 0.01). Sucrase activity in the small intestine and cecum was decreased significantly by maltitol (p < 0.05, p < 0.01) or glucomannan (p < 0.01, p < 0.01) ingestion, whereas it was not decreased in the colon. Maltitol hydrolyzing activity did not decrease significantly in the small intestine of the maltitol group, although that in the cecum and colon was not measured exactly by the methods used here. These results demonstrate that disaccharidases exist in the cecal and colonic mucosa of rat, and that they are not induced even in the tissue with hyperplasia, which is caused by maltitol ingestion.

Animals↗
PubMed2001

[Bacterial translocation associated with short bowel: role of ileocecal valve and cecum].

Sepsis in short bowel syndrome (SBS) is due in part to bacterial translocation (BT). Parenteral nutrition (PN) is often necessary in SBS and promotes BT. The presence of ileocecal valve (ICV) has been considered as a good prognostic factor in the outcome of this children. The aim of this study was to asses the effect of the presence or absence of ICV and cecum in five different models of gut resection in the rat. Fifty-five adult Wistar rats were randomly assigned to one of five groups: Group 1 (N = 14): standard rat chow + 80% small bowel resection. Group 2 (N = 10): standard rat chow + 80% small bowel resection including cecum. Group 3 (N = 10): standard rat chow + 80% small bowel resection including ICV. Group 4 (N = 11): NP + 80% small bowel resection. Group 5 (N = 10): NP + 80% small bowel resection including ICV and cecum. Ten days after surgery they were sacrificed and mesenteric lymph nodes (MLN), spleen and peripheral (PBL) and portal blood (POBL) specimens were recovered and cultured. Groups 3 (without ICV, with cecum) and 5 (without ICV, without cecum) showed 60% BT in MLN and POBL, and groups 1 and 4 (with ICV, without cecum) 93% and 91% respectively (p < 0.05). In PBL, group 3 (without ICV, with cecum) showed also less BT than groups 1 and 4 (10% vs 43% and 55% respectively, p < 0.05) and group 5 (without ICV and cecum) had less BT than groups 1, 2 and 4 (0% vs 43%, 30% and 55%, p < 0.01). In conclusion, these results suggest that the absence of ICV decreases BT and that the cecum does not seems to play a role on his.

Animals↗
PubMed2000

The human gut bacteria Bacteroides thetaiotaomicron and Fusobacterium varium produce putrescine and spermidine in cecum of pectin-fed gnotobiotic rats.

Pectin is a soluble indigestible polysaccharide that stimulates cecal polyamine formation in rats. Bacteroides and fusobacteria, two numerically dominant bacterial population groups in the large intestine, were found to synthesize in vitro high amounts of spermidine and putrescine. The purpose of this study was to elucidate the effect of pectin on the polyamine production by defined bacterial species in vivo. Germfree male Wistar rats (n = 18) were randomly assigned to one of three treatments: (i) monoassociation with Bacteroides thetaiotaomicron + fiber-free diet; (ii) diassociation with B. thetaiotaomicron + Fusobacterium varium + fiber-free diet or (iii) diassociation with B. thetaiotaomicron + F. varium + fiber-free diet + 10% pectin. The cecal contents of monoassociated rats fed fiber-free diet contained large amounts (1.51+/-0.21 micromol/dry total cecum content) of spermidine which was the major polyamine. The cecum of diassociated rats fed the fiber-free diet contained even higher concentrations of spermidine (2.53+/-0.21 micromol/dry total cecum content) and also putrescine, which was now the dominant polyamine (putrescine 0.32+/-0.28 vs. 3.01+/-0.28 micromol/dry total cecum content; monoassociation vs. diassociation). Pectin consumption by diassociated rats led to an additional increase in the cecal concentrations of all polyamines: putrescine, spermidine and spermine were 40, 37 and 100%, respectively, higher in the diassociated rats consuming the pectin diet than in those consuming the pectin-free diet. Since the microbial counts in the cecum did not differ in the diassociated treatment groups, the elevated concentrations of polyamines observed in the pectin group must have been due to stimulated bacterial polyamine synthesis. The decline of individual polyamines from cecum to feces detected at the end of the study in all treatment groups and the high microbial counts in the cecum and in feces suggest that bacterial polyamines are absorbed in cecum and colon. Pectin stimulates intestinal microbes to synthesize large amounts of polyamines which may be utilized by the host.

Analysis of Variance↗
PubMed1997

Myoelectric activity of the cecum and proximal loop of the ascending colon in cows after spontaneous cecal dilatation/dislocation.

OBJECTIVE: To analyze myoelectric activity of the cecum and proximal loop of the ascending colon (PLAC) in cows after spontaneous cecal dilatation/dislocation (CDD) and compare it with that in healthy cows after surgical evacuation of the cecum. ANIMALS: 12 cows with spontaneous CDD and 6 healthy cows (group C). Cows with spontaneous CDD were retrospectively assigned to 2 groups: delayed recovery from surgery or recurrence (group A; n = 3), and normal recovery (group B; n = 9). PROCEDURE: After surgical evacuation of the cecum, 8 pairs of bipolar, retrievable electrodes were implanted in the ileum, cecum, and PLAC. Cows were evaluated daily from postoperative day 1 to 7, using routine clinical methods and computer-based analysis of myoelectric activity of the cecum, and PLAC. Parameters of myoelectric activity included rate of spike bursts, duration of individual spike bursts, duration of overall spike burst activity per electrode, rate of propagated spike burst sequences, and ratio of orally propagated spike burst sequences. RESULTS: Rate of spike bursts, duration of cecocolic spike burst activity, and ratio of orally to aborally propagated spike burst sequences did not vary among groups during the 7-day recording period. However, cows with delayed recovery had a typical, uniform pattern of myoelectric activity of the cecum and PLAC at days 1 and 2 after surgery that consisted of repeated, propagated spike burst sequences, made up of spike bursts of significantly (P < 0.05) increased duration at postsurgical day 1 and substantially prolonged duration at postsurgical day 2, interrupted by periods of little or no activity. CONCLUSION: Delayed recovery and recurrence of CDD in cows after spontaneous CDD is not caused by hypomotility of the cecum and PLAC. CLINICAL RELEVANCE: Postoperative treatment, intended to reduce recurrence of CDD or delayed recovery after surgical evacuation of the cecum, should address propagation of digesta in the spiral colon.

Animals↗
PubMed1987

Relation between alpha-methyl-D-glucoside influx and brush border surface area in enterocytes from chicken cecum and jejunum.

We have investigated the possible relation between the phloridzin-sensitive influx of alpha-methyl-D-glucoside (concentration 5 mmol/l) and the brush border surface area, in chicken isolated enterocytes. The intestinal regions studied were: jejunum and proximal cecum (both with high affinity sugar transport sites), medial cecum (with a low affinity transport system) and distal cecum (which lacks any transport ability). Cell apical surface measured by electron microscopy gave the following results; jejunal cells (0.41 micron 2) greater than proximal cecal cells (0.23 micron 2) greater than medial cecal cells (0.15 micron 2) = distal cecal cells (0.14 micron 2). This parameter is mainly determined by the length of microvilli. Sugar influx studies showed that the concentration of the substrate in cell water (in mmol/l) was jejunum (7.1) greater than proximal cecum (2.9) greater than medial cecum (1.7) greater than distal cecum (not different from zero). The decline in influx rate from proximal to distal cecum may be explained both by changes in surface and by the different carriers involved (different Km). Results of sugar concentration in the distal cecal cells do not correlate with the other segments studied since the substrate enters in these cells by a passive process. It is concluded that the degree of development of microvilli should be taken into account when estimating nutrient transport rates in different intestinal segments.

Animals↗
PubMed1999

Ion transport across the cecum in normal and colitic mice.

This study was conducted to determine the ion transport mechanisms in the normal mouse cecum and compare them to an inbred mouse model of colitis. The Ussing chamber-voltage clamp technique was used to monitor the short circuit current (I(sc)). The basal I(sc) in the normal cecum was 82.6 +/- 5.8 microA/cm2. It was not affected by bumetanide, 9-anthracene carboxylate, amiloride, and phenamil or by removal of Cl- ions; but was abolished by the removal of Na+ ions. Flux measurements revealed the presence of neutral NaCl transport. In the colitic cecum, the basal current was significantly higher than the normal cecum. Basal current in the normal cecum was due primarily to Na+ absorption through a Na+ channel, while in the colitic cecum it was due to Cl- ion secretion. cAMP addition in colitic cecum did not increase Cl- secretion, further suggesting that the tissue is already secreting at a maximal rate.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1992

Cigarette smoking and nicotine delay postprandial mouth-cecum transit time.

The acute effects of both cigarette smoking and nicotine on postprandial mouth-cecum transit were studied in 20 habitual smokers, 10 males and 10 females. Mouth-cecum transit time was measured by the breath hydrogen technique, following ingestion of a standard mixed liquid meal. Each subject was studied on four separate occasions, either (1) sham or actively smoking two standard cigarettes, commencing 20 min after the meal, or (2) chewing two placebo or nicotine tablets over a 60-min period, commencing immediately after the meal. The time of administration of these stimuli was designed to minimize the effects on mouth-cecum transit time of alterations in gastric emptying. Mouth-cecum transit time was prolonged in response to both smoking [median and interquartile range: 120 (95, 150) min vs 100 (75, 140) min, P = 0.01] and nicotine [120 (80, 170) min vs 100 (70, 140) min, P = 0.002]. No difference was observed between sexes with respect to nicotine; the effect of smoking on mouth-cecum transit time, however, was less pronounced in females compared to males [difference active-placebo: 10 (10, 20) min vs 35 (20, 60) min, P = 0.01]. We conclude that acute cigarette smoking delays mouth-cecum transit time, an effect most likely due to nicotine.

Adult↗