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  • Author or Editor: Jürg W. Blum x
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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.

Full access
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)

Full access
in American Journal of Veterinary Research

Abstract

Objective—To describe the distribution of mRNA that codes for 9 subtypes of adrenergic receptors in the digestive tract of dairy cows.

Sample Population—Fresh full-thickness wall specimens from the abomasum (fundus, corpus, and antrum), ileum, cecum, proximal loop of ascending colon, and 4 locations of the spiral colon collected from 10 healthy cows at slaughter.

Procedure—Concentrations of mRNA that code for 9 subtypes of adrenergic receptors in the bovine gastrointestinal tract (α1A, α1B, α1D, α2AD, α2B, α2C, β1, β2, and β3) were measured by use of a quantitative realtime reverse transcription-polymerase chain reaction assay. Results were reported in relation to mRNA expression of the housekeeping gene glyceraldehyde phosphate dehydrogenase (GAPDH).

Results—Mean mRNA contents of adrenergic receptors in the bovine digestive tract were low (range, 0.00006% to 5.04% of GAPDH). Distribution of receptor subtypes was similar in all tissues, with lowest expression of α1D receptors, followed by α2B, α2C, β3, α1B, α1A, β1, and β2 in the abomasum, whereas α2AD and β2 in the intestines were highest. In comparison with the intestines, relative concentrations of mRNA for receptors β2 and β3 were significantly lower in the abomasum.

Conclusions and Clinical Relevance—Relative concentrations of mRNA that code for adrenergic receptors differed among receptor subtypes and among locations in the bovine gastrointestinal tract. Comparison of these values established in healthy cattle with results for cows with motility disorders, such as abomasal displacement and cecal dilatation, may lead to improved therapeutic or prophylactic approaches for these diseases. (Am J Vet Res 2004;65:1142–1150)

Full access
in American Journal of Veterinary Research

Abstract

Objective—To describe the distribution of mRNA that codes for 8 subtypes of 5-hydroxytryptamine receptors (5-HTRs) in the digestive tract of dairy cows.

Sample Population—Fresh full-thickness wall specimens from the abomasum (fundus, corpus, and antrum), ileum, cecum, proximal loop of ascending colon, and 4 locations of the spiral colon collected from 10 healthy cows at slaughter.

Procedure—Concentrations of mRNA that code for 5-HTR subtypes (5-HTR1A, 5-HTR1B, 5-HTR1D, 5-HTR1F, 5-HTR2A, 5-HTR2B, 5-HTR2C, and 5-HTR4) in the bovine digestive tract were measured by use of a quantitative real-time reverse transcription-polymerase chain reaction assay. Results were reported in relation to mRNA expression of the housekeeping gene glyceraldehyde phosphate dehydrogenase (GAPDH).

Results—Mean relative mRNA concentrations for 5-HTR were low (range, 0% to 1.32% of GAPDH), and mRNA that codes for 5-HTR1A was not detected. In the abomasum, mRNA expression was highest for 5-HTR1B and 5-HTR2B, followed by subtypes 1F, 2A, 1D, and 4, whereas 5-HTR2C was not detected. In intestinal samples, concentrations of subtypes 1B, 2B, and 4 were highest, followed by 1D, 1F, 2A, and 2C. Relative concentrations of mRNA that code for 5-HTR2A were significantly higher in the abomasum than the intestines, but lower for 5-HTR2B, 5-HTR2C, and 5-HTR4.

Conclusions and Clinical Relevance—Relative concentrations of mRNA that code for 5-HTRs differ among locations in the gastrointestinal tract of cattle. Understanding differences in the distribution of 5- HTRs in healthy cattle and cattle with gastrointestinal tract disease may lead to improved therapeutic approaches for abomasal and cecal motility disorders. (Am J Vet Res 2004;65:1151–1158)

Full access
in American Journal of Veterinary Research

Abstract

Objective—To use threshold concentrations of acetone and β-hydroxybutyrate in milk and serum, respectively; identify risk for ketosis and endometritis; and assess analyses of blood and milk samples as predictors of risk for ketosis in high-yielding dairy cows.

Animals—90 multiparous Holstein cows.

Procedure—At intervals before and after parturition, blood samples were obtained for determination of glucose, nonesterified fatty acids, leptin, insulin, insulin-like growth factor-1, and β-hydroxybutyrate concentrations. Samples of milk were obtained at similar intervals after parturition for determination of fat content and concentrations of acetone, protein, and lactose. Reproductive examination of each cow was performed weekly.

Results—For each cow, threshold concentrations of acetone and β-hydroxybutyrate were calculated as 75th and 90th percentiles of maximum postpartum concentrations of acetone in milk (0.40 and 0.87 mmol/L) and β-hydroxybutyrate in serum (2.30 and 3.51 mmol/L). Significant decrease in milk production (442 to 654 kg of energy-corrected milk/305-day period per cow) was associated with acetone or β-hydroxybutyrate in excess of threshold values. Milk acetone concentrations > 0.40 mmol/L were associated with 3.2 times higher risk for endometritis. Low plasma glucose, high serum β-hydroxybutyrate, and high milk acetone concentrations during week 1 after parturition were indicators of increased risk for ketosis later during lactation.

Conclusions and Clinical Relevance—Determination of milk acetone concentration during the week after parturition may identify cows at risk for ketosis and endometritis; with appropriate interventions, development of disease and production losses may be reduced. (Am J Vet Res 2003:64:188–194)

Full access
in American Journal of Veterinary Research

Abstract

Objective—To investigate the distribution of mRNA coding for 7 subtypes of 5-hydroxytryptamine receptors (5-HTRs) in the intestines of healthy dairy cows and dairy cows with cecal dilatation-dislocation (CDD).

Sample Population—Full-thickness intestinal wall biopsy specimens were obtained from the ileum, cecum, proximal loop of the ascending colon, and external loop of the spiral colon (ELSC) of 15 cows with CDD (group 1) and 15 healthy dairy cows allocated to 2 control groups (specimens collected during routine laparotomy [group 2] or after cows were slaughtered [group 3]).

Procedure—Amounts of mRNA coding for 7 subtypes of 5-HTRs (5-HT1A, 5-HT1B, 5-HT1D, 5-HT1F, 5-HT2A, 5-HT2B, and 5-HT4) were measured by quantitative real-time reverse transcriptase–PCR assay. Results were expressed as the percentage of mRNA expression of a housekeeping gene.

Results—Expression of mRNA coding for 5-HTR1B, 5-HTR2B, and 5-HTR4 was significantly lower in cows with CDD than in healthy cows. For 5-HTR2B and 5-HTR4, significant differences between cows with CDD and control cows were most pronounced for the ELSC. Expression of mRNA for 5-HTR1D, 5-HTR1F, and 5-HTR2A was extremely low in all groups, and mRNA for 5-HTR1A was not detected.

Conclusions and Clinical Relevance—Relative concentrations of mRNA coding for 5-HTR1B, 5-HT2B, and 5-HTR4 were significantly lower in the intestines of cows with CDD than in the intestines of healthy dairy cows, especially for 5-HT2B and 5-HTR4 in the ELSC. This supports the hypothesis that serotonergic mechanisms, primarily in the spiral colon, are implicated in the pathogenesis of CDD.

Full access
in American Journal of Veterinary Research

Abstract

Objective—To investigate the distribution of mRNA coding for 9 adrenoceptor subtypes in the intestines of healthy dairy cows and cows with cecal dilatationdislocation (CDD).

Sample Population—Full-thickness specimens of the intestinal wall were obtained from the ileum, cecum, proximal loop of the ascending colon (PLAC), and external loop of the spiral colon (ELSC) of 15 cows with CDD (group 1) and 15 healthy (control) cows (group 2, specimens collected during laparotomy; group 3, specimens collected after slaughter).

Procedures—Concentrations of mRNA for 9 adrenoceptor subtypes (α1A, α1B, α1D, α2AD, α2B, α2C, β1, β2, and β3) were measured by quantitative real-time reverse transcriptase-PCR assay. Results were expressed relative to mRNA expression of a housekeeping gene.

Results—Expression of mRNA for α1B-, α2AD-, α2B-, β1-, and β2-adrenoceptors was significantly lower in cows with CDD than in control cows. In the ileum, these receptors all had lower mRNA expression in cows with CDD than in control cows. The same effect was detected in the ELSC for mRNA for α2AD-, α2B-, β1-, and β2-adrenoceptors, and in the cecum and PLAC for α2B- and β2-adrenoceptors. Groups did not differ significantly for α1A-adrenoceptors. The mRNA expression for α1D-, α2C-, and β3-adrenoceptors was extremely low in all groups.

Conclusions and Clinical Relevance—Differences in expression of mRNA coding for adrenoceptors, most pronounced in the ileum and spiral colon, between cows with CDD and control cows support the hypothesis of an implication of adrenergic mechanisms in the pathogenesis of CDD in dairy cows.

Full access
in American Journal of Veterinary Research