Expression of messenger RNA coding for 5-HT receptor, alpha and beta adrenoreceptor (subtypes) during oestrus and dioestrus in the bovine uterus

Serotoninergic and adrenergic receptors (5-HTR and AR) are involved in the regulation of uterine contractility. The objective of this study was to compare mRNA levels of 5-HTR(1A), 5-HTR(1B), 5-HTR(1D), 5-HTR(1F), 5-HTR(2A), 5-HTR(2B), 5-HTR(2C), 5-HTR(4) and alpha(1A), alpha(1B), alpha(1D), alpha(2AD), alpha(2B), alpha(2C), and beta(1), beta(2), beta(3)-AR in oestrus and dioestrus, and at three uterine locations (tip, middle and base) using quantitative real-time polymerase chain reaction. Uterine specimens consisting of endometrium and myometrium including vessels and serosa were collected from cows in oestrus (n = 10) and dioestrus (n = 15) respectively. Levels of 5-HTR and AR mRNA were expressed relative to the geometric mean of ribosomal RNA (18S), ubiquitin and glyceraldehyde phosphate dehydrogenase by the mean values of geNorm algorithm. 5-HTR(1A), 5-HTR(2C) and beta(3)-AR mRNA could not be detected in uterine tissues. The mRNA levels of 5-HTR(1F) and 5-HTR(2B) were lower (P < 0.05), but of 5-HTR(4) were higher (P < 0.05) in oestrus than in dioestrus. The mRNA levels of alpha(1A)-AR, alpha(2AD)-AR, alpha(2B)-AR were lower (P < 0.05), but of alpha(2C)-AR and beta(2)-AR were higher (P < 0.05) in oestrus than dioestrus. The mRNA levels of 5-HTR(1B) and 5-HTR(1D) (oestrus) and of alpha(2AD)-AR (dioestrus) differed among uterine locations (base > middle > tip; P < 0.05). The mRNA expression of 5-HTR and AR (subtypes) in bovine uterus was associated with cycle activity and varied according to uterine location. Additional studies on protein level will be carried out in order to elucidate the role of these receptor families on uterine contractility, which may then help to clarify clinical relevance.     

Distribution of muscarinic receptor subtypes and interstitial cells of Cajal in the gastrointestinal tract of healthy dairy cows

OBJECTIVE: To describe the distribution of muscarinic receptor subtypes M(1) to M(5) 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 M(1) receptors was found in the submucosal plexus and myenteric plexus. Antibodies against M(2) receptors stained nuclei of smooth muscle cells only. Evidence of M(3) 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 M(4) receptors. Staining for M(5) 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 M(1), M(3), M(5), 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.     

Effects of physiological state and body fatness on digestive-tract weight and composition in the dairy cow

Sixteen Holstein-Friesian cows were slaughtered in the following physiological situations: dry and very lean (Group 1); dry and fat (Group 2); after one week of lactation and fat (Group 3); after eight weeks of lactation and very lean (Group 4). Weights of emptied reticulo-rumen, omasum, abomasum and intestines, amounts of protein and minerals in the whole digestive tract, and apparent area of reticulo-rumen were measured. Bone weight was taken as an estimate of mature body size, independent of body-fat reserves.Physiological state had no effect on digestive-tract weight and composition. Abomasum, intestine and whole tract weights were related to body fatness, but the weights of the tract excluding lipids, and estimated amounts of protein and minerals were not. The digestive tract was not significantly involved in protein and mineral mobilization or deposition. The apparent area of the reticulo-rumen varied slightly between the first and eighth weeks of lactation. Reticulo-rumen and abomasum weights were positively related to cow size.     

Are so many adrenergic receptor subtypes really present in domestic animal tissues? A pharmacological perspective

Adrenergic receptors (ARs) are the cellular membrane binding sites through which natural catecholamines and sympathomimetic drugs exert their physiological and pharmacological effects. In recent decades, studies to clarify the distribution and function of ARs have been performed mostly on cultured cells, laboratory animals and human target tissues, but little is known about these aspects in domestic animals. This review focuses on AR structure, classification and signalling pathways and on AR subtype distribution in target tissues of some domestic animals, namely dogs, horses and bovines. In these species, different alpha- and beta-AR subtypes have been characterized and the functions controlled by the adrenergic systems have been studied. In the dog, the role played by the adrenergic system in the pathogenesis of cardiovascular disorders and in the modulation of canine aggression has roused particular interest. In dogs affected by dilated cardiomyopathy a significant down-regulation of beta-ARs has been observed both in the heart and circulating lymphocytes. This finding confirms the involvement of the adrenergic system in the pathogenesis and progression of the disorder and suggests new therapeutic strategies. In the horse, AR distribution has been studied in the cardiac, respiratory and gastrointestinal systems as well as in digital veins and arteries. The cardiac beta-ARs in healthy horses seem to be predominantly represented by the beta(1) subtype. In this species, heart failure may increase the expression of the beta(2) subtype, rather than causing AR down-regulation. Different beta- and alpha-AR subtypes have been characterized in the smooth muscle of equine ileum. The sympathetic relaxation of equine ileum smooth muscle seems to depend mainly on beta(3)-AR subtype activation, with minor involvement of the beta(2) subtype. In the respiratory tract, regional differences have been evidenced in the functionality of beta-AR subtype. The beta(2) subtype predominates in all segments but the beta(2) subtype-mediated adenyl cyclase response is tissue-dependent, with higher activity in tracheal membranes than bronchial or pulmonary ones. Both alpha- and beta-AR subtypes are present in the genital tract of cows. Bovine ovarian and myometrial cell membranes express higher concentrations of beta(2)-ARs than the beta(1) subtype, whereas as far as alpha-ARs are concerned, a single class of alpha(1)-ARs and two distinct classes of alpha(2)-AR binding sites have been discriminated. Interestingly, it has been observed that the activation of the sympathetic system could play an important role in the pathogenesis of bovine ovarian cysts as suggested by the modifications in beta-AR levels in the hypophysis and ovary of cows affected by ovarian cysts. In this species, the phenomenon of down-regulation has been well studied in different organs of veal calves treated with clenbuterol as a "partitioning agent". Since differences exist in AR distribution among species, data obtained in laboratory animals or in human beings cannot be extrapolated to domestic animals and further investigation on AR subtypes in domestic animal tissues is necessary.     

New perspectives in cardiopulmonary therapeutics: receptor-selective adrenergic drugs

Recent advances in basic biomedical research have led to the development of clinically useful drugs known as "second generation" adrenergic receptor stimulants (agonists) and blockers (antagonists). Adrenergic receptors are now differentiated into 4 distinct subtypes: alpha 1, alpha 2, beta 1, and beta 2. The new drugs are more receptor-selective and tissue-specific than older ones and, hence, have increased potential for directed therapeutic action, with relatively less side effects on nontargeted organs. The beta 2-selective agonist terbutaline, eg, causes bronchodilation with less beta 1-cardiac excitation than does the beta 1-beta 2 nonselective agonist isoproterenol. Compared with the latter, the beta 1-selective agonist dobutamine increases myocardial contractile force and cardiac output with less beta 2-mediated vasodilation and hypotension. The beta 1-selective antagonist metoprolol has advantage over the beta 1-beta 2 nonselective blocker propranolol for controlling beta 1-cardiac excitation in patients with compromised pulmonary function. Prazosin, an alpha 1-selective blocking agent, evokes peripheral vasodilation with less reflex tachycardia than does the nonselective alpha 1-alpha 2 blocker phentolamine, probably because the former spares the prejunctional alpha 2-receptors that subserve autoinhibition of norepinephrine release from the sympathetic neuron. The contemporary practice of internal medicine will no doubt include an understanding of the pharmacologic properties associated with the various adrenergic receptor subtypes.     

Myoelectric activity in the intestines of healthy dairy cows during the recovery period after implantation of permanent electrodes

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 steady-state 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.     

The use of ultrasonography for diagnosing the cause of colic in cows. A review

Ultrasonography is a very useful technique for diagnosing the cause of colic in cows. It allows visualisation of abnormal reticular contour and occasionally of abnormal contractility in cows with reticuloperitonitis. In right-displaced abomasum, the dilated abomasum can be detected between the right abdominal wall and the liver. Fluid ingesta are seen ventrally and a gas cap of varying size dorsally. Dilated loops of small intestines that are almost always static are the main diagnostic criterion for ileus of the small intestine, but the cause of the ileus can only rarely be determined. Cholestasis can almost always be diagnosed by imaging a dilated biliary system. With obstruction at the level of the hepatic portal, only the intrahepatic biliary ducts are dilated, while a dilatation of the entire biliary tract, including the gallbladder, occurs in the case of an obstruction near the duodenal papilla. Urinary tract diseases cause colic in cows when concrement or inflammatory products become lodged in a ureter. The importance of ultrasonography in the diagnosis of diseases causing colic in cows varies. For example, with colic attributable to ileus of the small intestines, cholestasis or urinary tract disease, ultrasonography is a very useful diagnostic tool. On the other hand, for diagnosis of left or right displacement of the abomasum or caecal dilatation, ultrasonography is generally not required, but it is helpful in difficult cases to confirm or rule out a tentative diagnosis and to avoid an unnecessary exploratory laparotomy.     

The particulate passage rate,nutrient composition and fermentation characteristics across gastrointestinal tracts in lactating dairy cows fed three different forage source diets

This study was conducted to investigate the particulate passage rate, nutrient characteristics and fermentation parameters across the gastrointestinal tract (GIT) in lactating dairy cows fed cereal straws in comparison with alfalfa hay. Eighteen multiparous Holstein cows were randomly assigned to one of three experimental diets consisting of 55% concentrate, 15% corn silage and 30% different forage sources as follows (% of dry matter [DM]): (i) 23% alfalfa hay and 7% Chinese wild rye hay (AH); (ii) 30% corn stover (CS); and (iii) 30% rice straw (RS). The Cr‐mordanted corn silage‐neutral detergent fibre was used to estimate the passage flow at week 14. After 14‐week feeding, the animals were slaughtered to collect the gastrointestinal digesta. Dietary forage sources had little effect on the fractional passage rates in the rumen (range from 5.05 to 6.25%/hr) or hindgut (range from 4.49 to 5.24%/hr). Total volatile fatty acid (VFA) concentration in the caecum was highest, followed by the rumen, colon and rectum, and the lowest in the abomasum and duodenum, indicating that the large intestines, especially caecum, are the important positions for carbohydrate degradation. Greater proportion of propionate and butyrate and lower acetate were found in the AH compared to CS or RS in colon, but higher acetate in abomasum was found in the cows fed CS or RS compared to AH. In conclusion, cereal straw diets did not change the particulate passage rate in the rumen and hindgut which might be mainly due to the similar DM intake among these three diets. Different forage source diets significantly changed VFA proportion in the abomasum and colon, indicating the existence of different digestion or absorption rates in these tracts among the experimental diets.     

Torsion of the abomasum in ruminants: Diagrammatic representation of rotary movements based on post-mortem findings

Summary A theoretical analysis of the types of displacement of the abomasum in the abdomen is presented based on a stud of forty-seven post-mortem examinations of calves, cows, lambs and sheep showing right-sided abomasal displacement and production of knots. These displacements are quantified following the introduction of a dual-axial system. One system (XYZ) related to displacements of the abomasum on a pendulum model, the point of suspension being situated on the visceral surface of the liver and the arms consisting of parts of the digestive tract adjacent to the abomasum. The other system (x (1) y (1)z(1) ) comprises axes centered on the abomasum, about which this organ was able to rotate without changing its position in the abdomen. In order to make quantification of the displacements and deformations possible, the term twine is introduced. Twining results from interlacing of sections of the digestive tract, which are not normally adjacent. This limits the concept of torsion to helices appearing in the pyloro-duodenal region and the omaso-abomasal junction. To identify the various forms of abomasal displacement, a new terminology is introduced and basic elements suggested to make quantifications possible.     

Ontogenesis of mRNA levels and binding sites of hepatic alpha-adrenoceptors in young cattle

Catecholamines affect hepatic glucose production through (alpha- and beta2-) adrenoceptors (AR). We studied mRNA abundance and binding of hepatic alpha-AR in pre-term (P0) calves and in full-term calves at day 0 (F0), day 5 (F5) and day 159 (F159) to test the hypothesis that gene expression and numbers of hepatic alpha-AR in calves are influenced by age and associated with beta2-AR and selected traits of glucose metabolism. mRNA levels of alpha1- and alpha2-AR were measured by real time RT-PCR. alpha1- and alpha2-AR numbers (maximal binding, Bmax) were determined by saturation binding of (3H)-prazosin and (3H)-RX821002, respectively. alpha1- and alpha2-AR subtypes were evaluated by competitive binding. alpha1A-AR mRNA levels were lower in P0 than in F0, F5 and F159 and alpha(2AD)-AR mRNA levels were lower in F159 than in P0, F0 and F5, while alpha2C-AR mRNA levels increased from P0 and F0 to F5 and F159. Bmax of alpha1-AR increased from P0 to F5, then decreased in F159. Bmax of alpha2-AR decreased from F0 to F159. Bmax of alpha1-AR was positively associated with mRNA levels of alpha1A-AR (r = 0.7), Bmax of beta2-AR (r = 0.5) and negatively with hepatic glycogen content (r = -0.6). Bmax of alpha2-AR was negatively associated with Bmax of beta2-AR (r = -0.4). In conclusion, mRNA levels and binding sites of alpha1- and alpha2-AR in calves exhibited developmental changes and were negatively associated with hepatic glycogen content.     

Quantitative mRNA analysis of muscarinic acetylcholine receptors in the intestine of dairy cows with spontaneous caecal dilatation-dislocation

Muscarinic receptors mediate acetylcholine-induced muscular contractions. In this study, mRNA levels of muscarinic receptor subtypes 2 and 3 (M(2) and M(3)) in the ileum, caecum, proximal loop of the ascending colon (PLAC) and external loop of the spiral colon (ELSC) were determined by quantitative polymerase chain reaction in seven cows with caecal dilatation-dislocation (CDD) and seven healthy control cows. Levels of M(2) were significantly lower in the caecum, PLAC and ELSC and levels of M(3) were significantly lower in the ileum, caecum, PLAC and ELSC of cows with CDD compared to healthy cows (P<0.05). Down-regulation of M(3) may play a role in the pathogenesis of CDD.     

Ultrasonographic examination of the omasum, liver, and small and large intestines in cows with right displacement of the abomasum and abomasal volvulus

OBJECTIVE: To describe ultrasonographic appearance of the liver, small and large intestines, and omasum in cows with right displacement of the abomasum (RDA) and with abomasal volvulus (AV) and to determine whether RDA and AV can be differentiated on the basis of ultrasonographic findings. ANIMALS: 17 cows with RDA, 9 cows with AV, and 10 healthy control cows. PROCEDURES: A linear transducer was used to examine the abomasum, liver, omasum, and small and large intestines from the right side. Results-The liver was imaged less frequently in cows with RDA or AV, compared with control cows. In 9 cows with RDA or AV, the liver could not be imaged. The small intestine was imaged less frequently in cows with RDA or AV than in control cows; in cows with AV, the small intestine could not be imaged in the 8th, 9th, or 10th intercostal space. The large intestine was imaged less frequently in the 11th and 12th intercostal spaces and the cranial region of the flank in cows with RDA or AV. The omasum was also imaged less frequently in the 8th and 9th intercostal spaces in cows with RDA or AV. Cows with RDA or AV could not be differentiated on the basis of ultrasonographic findings. CONCLUSIONS AND CLINICAL RELEVANCE: Compared with control cows, cows with RDA and AV had changes in positioning and therefore extent of ultrasonographic imaging of the liver, omasum, and small and large intestines; however, these findings were not useful in differentiating between cows with RDA and AV.