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  • Author or Editor: Mireille Meylan x
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Abstract

Objective—To describe myoelectric activity of the spiral colon in healthy cows.

Animals—7 lactating Simmental X Red-Holstein crossbred cows.

Procedure—Cows were implanted with 7 pairs of bipolar silver electrodes (4 in the spiral colon and 1 each in the cecum, distal part of the ileum, and proximal loop of the ascending colon [PLAC]). Myo-electric activity was recorded during 4 days for each cow. Patterns were analyzed, using computer-based methods.

Results—Myoelectric activity of the spiral colon was closely associated with motility of the ileum and PLAC and showed the typical organization of migrating myoelectric complexes (MMC). The MMC in the bovine spiral colon (bcMMC) had a mean ± SD duration of 188.6 ± 30.8 minutes and was divided into 4 phases. Phases I and II lasted 11.3 ± 1.4 and 159.4 ± 33.3 minutes, respectively. Phase III (duration, 5.4 ± 1.2 minutes) was characterized by 5.2 ± 0.9 regular spindles (35.4 ± 5.4 seconds) and 1 final elongated spindle (137.2 ± 56.4 seconds). Phase III most commonly (73.8 ± 16.1%) was followed by phase IV (duration, 17.3 ± 3.6 minutes). Propagation velocity of phase III was 4.4 ± 0.5 cm/min, and 13.6% of bcMMC were incompletely propagated through the spiral colon.

Conclusion and Clinical Relevance—Myoelectric activity of the bovine spiral colon is composed of a recurring cyclic pattern similar to MMC of the small intestine. Data of colonic myoelectric activity in healthy cows will serve as a basis for studies on cecal dilatation and dislocation in cattle. (Am J Vet Res 2002;63:78–93)

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in American Journal of Veterinary Research

Abstract

Objective—To describe myoelectric patterns in the intestines of cows after electrode implantation.

Animals—7 lactating Simmental-Red Holstein cows.

Procedure—Cows were implanted with 7 pairs of bipolar silver electrodes (1 each in the ileum, cecum, and proximal loop of the ascending colon (PLAC) and 4 in the spiral colon). Myoelectric activity was monitored during 10 periods within the first 3 weeks after surgery. Recordings from the first 2 weeks were compared with recordings from the third week, which was considered a steady-state condition.

Results—Significant changes over time were detected for 18 of 57 variables, including 3 variables describing myoelectric activity of the ileum, 6 variables of the cecum, 6 variables of the PLAC, and 3 variables of the spiral colon. Compared with values for the steadystate condition, 16 variables differed significantly for the 14-day period after surgery (7 variables until day 11, 2 variables until day 8, 4 variables until day 5, 1 variable until day 3, and 2 variables until day 2 after electrode implantation). None of the variables had significant changes that lasted only 1 day after surgery.

Conclusions and Clinical Relevance—Significant changes were observed for several variables of myoelectric activity in all intestinal segments until as late as 11 days after electrode implantation, whereas a steady-state condition was reached 14 days after surgery. Effects of drugs, manipulations, or nutrition regimens on myoelectric activity of the bovine digestive tract should be evaluated no sooner than 2 weeks after electrode implantation. (Am J Vet Res 2004;65:797–805)

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in American Journal of Veterinary Research

Abstract

Objective—To characterize and compare in vitro contractility patterns of sections of abomasal wall harvested from cattle of 3 dairy breeds.

Sample Population—Longitudinal and circular smooth muscle preparations harvested from the antrum and body of the abomasum of 30 recently slaughtered Holstein-Friesian, Brown Swiss, and Simmental X Red Holstein cows.

Procedure—Spontaneous isometric contractions of specimens in tissue baths of modified Krebs solution were recorded during a 4-hour period. Maximal amplitude, frequency of contractions, and change of basal tension were used to characterize contractility. Statistical analyses were used to test for differences among time periods, among breeds, between specimen locations, and between fiber orientations.

Results—Myoactivity patterns of abomasal smooth muscle preparations are highly variable and differ on the basis of location and fiber orientation. Frequency of contractions differed significantly among time periods for longitudinally oriented specimens with decreasing frequencies of contractions over time. Maximal amplitude of the longitudinally oriented specimens from the antrum increased significantly, whereas maximal amplitude of the circularly oriented specimens from the antrum decreased significantly. Values did not differ significantly among breeds.

Conclusions and Clinical Relevance—Patterns of spontaneous contractility of abomasal wall specimens are not homogeneous. During a 4-hour recording period, maximal amplitude and frequency of contractions of specimens varied significantly with respect to orientation and location; however, spontaneous contractile myoactivity did not differ significantly among breeds. Therefore, breed predisposition for displaced abomasum is not correlated with spontaneous activity of smooth muscle specimens. (Am J Vet Res 2002;63:1687–1694)

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in American Journal of Veterinary Research

Abstract

Objective—To describe the effects of an abrupt increase of concentrates in the diet of dairy cows on myoelectric activity of the spiral colon and on fermentation patterns in the rumen and large intestine.

Animals—6 healthy lactating Simmental X Red- Holstein cows.

Procedure—The diet of 6 cows implanted with bipolar electrodes in the spiral colon was changed from hay only to a ration of 50% hay:50% starch-rich concentrates during a period of 60 hours. Myoelectric activity of the spiral colon, concentrations of absolute and undissociated volatile fatty acids (VFA), and pH of ruminal and large intestinal contents were monitored before, during, and after the dietary change.

Results—Significant changes in patterns of myoelectric activity of the spiral colon were restricted to phases III and IV of the bovine migrating myoelectric complex and to propagation velocity. Significant alterations were not observed in pH or VFA concentrations in ruminal fluid, but pH decreased and VFA concentrations increased significantly in fecal specimens after the change of diet.

Conclusion and Clinical Relevance—Although rumen fluid is of limited value for measurement of certain indicators of fermentation, fecal samples can be used for measurement of pH and VFA concentrations, which serve as indicators of fermentation patterns in the large intestine. Increased concentrations of VFA and low pH in large intestinal digesta have a minimal influence on myoelectric activity of the spiral colon. Increased luminal VFA concentrations are unlikely to play an important role in the etiopathogenesis of motility disorders of the large intestine in cattle. (Am J Vet Res 2002;63:857–867)

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in American Journal of Veterinary Research

Abstract

Objective—To compare the effect of various concentrations of sodium butyric acid and sodium valerianic acid, as well as various osmolarities, on contractility of ex-vivo intestinal wall specimens obtained from the cecum and spiral colon of each of several healthy cows.

Sample Population—Full-thickness preparations of intestinal wall, dissected parallel to the longitudinal smooth muscle layers, harvested from freshly slaughtered healthy cows.

Procedure—Specimens of intestinal wall were incubated for 5 minutes with various concentrations of sodium butyric acid and sodium valerianic acid as well as various osmolar concentrations of NaCl, using a crossover design. Isometric contractions were induced 7 times with carbachol (CH; 5 X 10–6 mol/L). Contractility was defined as the maximum amplitude of contraction and the amplitude of contraction 2 minutes after addition of CH.

Results—Repeated addition of CH did not result in a significant effect on contractility of specimens from the cecum and spiral colon. Contractility after addition of CH was not significantly affected by prior incubation with various concentrations of sodium butyric acid or sodium valerianic acid or after an increase of osmolarity. Maximum amplitude of contraction was significantly higher in specimens from the spiral colon, compared with specimens from the cecum.

Conclusions—Increases in concentrations of sodium butyric acid or sodium valerianic acid and increases in osmolarity did not inhibit contractility of intestinal wall specimens from the cecum and spiral colon of a group of healthy cows. (Am J Vet Res 2000;61: 678–683)

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in American Journal of Veterinary Research

Abstract

Objective—To analyze myoelectric activity of the ileum, cecum, proximal loop of the ascending colon (PLAC), and spiral colon in cows with naturally occurring cecal dilatation-dislocation (CDD) and compare findings with those in healthy cows.

Animals—8 CDD-affected and 6 healthy control cows.

Procedures—Immediately after diagnosis, CDD-affected cows underwent surgery; control cows underwent a similar surgical procedure. Before completion of surgery, 8 bipolar silver electrodes were implanted in the ileum (n = 2), cecum (1), PLAC (1), and spiral colon (4) of each cow. Beginning the day after surgery, intestinal myoelectric activity was recorded daily (8-hour period) for 4 days; data were analyzed by use of specialized software programs. Quantitative variables of myoelectric activity were compared between groups.

Results—Cows of both groups recovered without complications after surgery. In control cows, physiologic myoelectric activity was recorded in all intestinal segments on all days after surgery. Apparently normal myoelectric activity was evident in the ileum of CDD-affected cows on the first day after surgery, but myoelectric activity patterns in the cecum, PLAC, and spiral colon were variable with no organized cyclic myoelectric patterns, incomplete or normally organized migrating myoelectric complexes, and slow normalization over time.

Conclusions and Clinical Relevance—After surgery for CDD, normal myoelectric patterns were disrupted in the large intestine of cows, especially in the spiral colon. Clinical recovery with effective transit of ingesta occurred before normalization of myoelectric activity in the large intestine. Therapeutic protocols for restoration or normalization of spiral colon motility should be developed for treatment of CDD-affected cattle.

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in American Journal of Veterinary Research

Abstract

Objective—To describe the in vitro effects of bethanechol on contractility of smooth muscle preparations from the small intestines of healthy cows and define the muscarinic receptor subtypes involved in mediating contraction.

Sample Population—Tissue samples from the duodenum and jejunum collected immediately after slaughter of 40 healthy cows.

Procedures—Cumulative concentration-response curves were determined for the muscarinic receptor agonist bethanechol with or without prior incubation with subtype-specific receptor antagonists in an organ bath. Effects of bethanechol and antagonists and the influence of intestinal location on basal tone, maximal amplitude (Amax), and area under the curve (AUC) were evaluated.

Results—Bethanechol induced a significant, concentration-dependent increase in all preparations and variables. The effect of bethanechol was more pronounced in jejunal than in duodenal samples and in circular than in longitudinal preparations. Significant inhibition of the effects of bethanechol was observed after prior incubation with muscarinic receptor subtype M3 antagonists (more commonly for basal tone than for Amax and AUC). The M2 receptor antagonists partly inhibited the response to bethanechol, especially for basal tone. The M3 receptor antagonists were generally more potent than the M2 receptor antagonists. In a protection experiment, an M3 receptor antagonist was less potent than when used in combination with an M2 receptor antagonist. Receptor antagonists for M1 and M4 did not affect contractility variables.

Conclusions and Clinical Relevance—Bethanechol acting on muscarinic receptor sub-types M2 and M3 may be of clinical use as a prokinetic drug for motility disorders of the duodenum and jejunum in dairy cows.

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in American Journal of Veterinary Research

Abstract

Objective—To describe the distribution of muscarinic receptor subtypes M1 to M5 and interstitial cells of Cajal (ICCs) in the gastrointestinal tract of healthy dairy cows.

Sample Population—Full-thickness samples were collected from the fundus, corpus, and pyloric part of the abomasum and from the duodenum, ileum, cecum, proximal loop of the ascending colon, and both external loops of the spiral colon of 5 healthy dairy cows after slaughter.

Procedures—Samples were fixed in paraformaldehyde and embedded in paraffin. Muscarinic receptor subtypes and ICCs were identified by immunohistochemical analysis.

Results—Staining for M1 receptors was found in the submucosal plexus and myenteric plexus. Antibodies against M2 receptors stained nuclei of smooth muscle cells only. Evidence of M3 receptors was found in the lamina propria, in intramuscular neuronal terminals, on intermuscular nerve fibers, and on myocytes of microvessels. There was no staining for M4 receptors. Staining for M5 receptors was evident in the myocytes of microvessels and in smooth muscle cells. The ICCs were detected in the myenteric plexus and within smooth muscle layers. Distribution among locations of the bovine gastrointestinal tract did not differ for muscarinic receptor subtypes or ICCs.

Conclusions and Clinical Relevance—The broad distribution of M1, M3, M5, and ICCs in the bovine gastrointestinal tract indicated that these components are likely to play an important role in the regulation of gastrointestinal tract motility in healthy dairy cows. Muscarinic receptors and ICCs may be implicated in the pathogenesis of motility disorders, such as abomasal displacement and cecal dilatation-dislocation.

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in American Journal of Veterinary Research

Abstract

Objective—To measure maximum binding capacity (Bmax) and levels of mRNA expression for α2-adrenergic receptor (AR) subtypes in ileal and colonic muscle layers of healthy dairy cows.

Sample Population—Ileal and colonic muscle specimens from 6 freshly slaughtered cows.

Procedures—Ileal and colonic muscle layers were obtained by scraping the mucosa and submucosa from full-thickness tissue specimens. Level of mRNA expression for α2-AR subtypes was measured by real-time reverse transcriptase-PCR analysis and expressed relative to the mean mRNA expression of glyceraldehyde phosphate dehydrogenase, ubiquitin, and 18S ribosomal RNA. Binding studies were performed with tritiated RX821002 (3H-RX821002) and subtype-selective ligands as competitors.

Results—mRNA expression for α2AD-, α2B-, and α2C-AR subtypes was similar in ileal and colonic muscle layers. The mRNA expression for α2AD-AR was significantly greater than that for α2B- and α2C-AR subtypes, representing 92%, 6%, and 2%, respectively, of the total mRNA. Binding competition of 3H-RX821002 with BRL44408, imiloxan, and MK-912 was best fitted by a 1-site model. The Bmax of α2AD- and α2C-AR sub-types was greater than that of α2B-AR. The Bmax and level of mRNA expression were only correlated (r = 0.8) for α2AD-AR. Ratio of Bmax to mRNA expression for α2C-AR was similar to that for α2B-AR, but significantly greater than for α2AD-AR.

Conclusions and Clinical Relevance—Subtypes of α2-AR in bovine intestinal muscle layers are represented by a mixture of α2AD- and α2C-ARs and of α2B-AR at a lower density. Information provided here may help in clarification of the role of AR subtypes in α2-adrenergic mechanisms regulating bovine intestinal motility.

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in American Journal of Veterinary Research

Abstract

OBJECTIVE To analyze the transit time from various locations in the intestines of cows with cecal dilatation-dislocation (CDD), healthy control cows, and cows with left displacement of the abomasum (LDA).

ANIMALS 15 cows with naturally occurring CDD (group 1), 14 healthy control cows (group 2), and 18 cows with LDA (group 3).

PROCEDURES 5 electronic transmitters were encased in capsules and placed in the lumen of the ileum, cecum, proximal portion of the colon, and 2 locations in the spiral colon (colon 1 and colon 2) and used to measure the transit time (ie, time between placement in the lumen and excretion of the capsules from the rectum). Excretion time of the capsules from each intestinal segment was compared among groups.

RESULTS Cows recovered well from surgery, except for 1 cow with relapse of CDD 4 days after surgery and 2 cows with incisional infection. High variability in capsule excretion times was observed for all examined intestinal segments in all groups. Significant differences were detected for the excretion time from the colon (greater in cows with CDD than in healthy control cows) and cecum (less in cows with LDA than in cows of the other 2 groups).

CONCLUSIONS AND CLINICAL RELEVANCE The technique developed to measure excretion time of capsules from bovine intestines was safe and reliable; however, the large variability observed for all intestinal segments and all groups would appear to be a limitation for its use in assessment of intestinal transit time of cattle in future studies.

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in American Journal of Veterinary Research