Effects of intraduodenal administration of tarazepide on pancreatic secretion and duodenal EMG in neonatal calves.

The influence of CCK-A receptor antagonism on pancreatic exocrine secretion and duodenal EMG, and the mechanism(s) involved in CCK-induced pancreatic secretion were studied in conscious calves. Seven 1-week-old calves were fitted with a pancreatic duct catheter, duodenal cannula and duodenal electrodes. Pancreatic exocrine secretion and duodenal EMG were studied following intraduodenal CCK-A receptor antagonist (Tarazepide), intravenous atropine, and intravenous or intraduodenal CCK-8 administrations. Tarazepide decreased duodenal electric activity, reduced interdigestive pancreatic secretion, especially protein; reduced cephalic and early postprandial (milk) induced secretion of bicarbonate and protein. Pancreatic protein secretion to intravenous CCK-8 was little affected by atropine, but was significantly reduced by Tarazepide+/-atropine; in contrast, protein secretion to intraduodenal CCK-8 was abolished by Tarazepide or atropine. We conclude that pre- and especially early postprandial pancreatic secretion are partly controlled via CCK-A (mainly mucosal) mediated mechanisms.

Comparative study of antibacterial activity of pancreatic juice in six mammalian species.

A comparative study of antibacterial activity of pancreatic juice was conducted on six mammalian species. Pancreatic juice collections were conducted as acute (rabbit, guinea pig, rat) and chronic (pig, sheep, cattle) experiments, in the former before and after stimulation [cholecystokinin (CCK) and secretin] and in the latter under basal conditions alone. Antibacterial activity was tested on Micrococcus pyogenes and compared with that of neomycin. The samples were tested under normal conditions and after heating and dilution. The pancreatic juice of rat showed no activity against Micrococcus pyogenes. The antibacterial activity of rabbit and guinea pig pancreatic juice under basal conditions was similar within the group but significantly higher than that of pig, sheep and cattle which also did not differ significantly within the group. On stimulation with CCK and secretin, no significant change could be observed in the potency of antimicrobial activity of pancreatic juice in the rabbit and guinea pig. The antibacterial activity remained unchanged after heating to 65 degrees C and upon dilution to 1:10.

Plasma amino acid indices and urinary 3-methyl histidine excretion in dairy cows in early lactation.

The experiment was performed on six cows from parturition to the 70th day of lactation. The highest milk yield, from 23 to 36 kg FCM daily, was reached between the 25th and the 50th day of lactation. The onset of lactation was accompanied with the intensification of muscle protein catabolism expressed by the highest urinary 3-methyl histidine excretion and body mass loss. In the same time the lowest plasma level of insulin, glucose, alanine, threonine, serine, proline, citrulline, ornithine, arginine, and urea was stated. The PDI intake covered PDI requirement at the beginning of lactation, 5th-10th day, but exceeded it in the period between 25th and 70th day of lactation. It caused the decrease of urinary 3-methyl histidine excretion and the increase of plasma urea cycle metabolites (ornithine, citrulline, arginine, urea) level.

Effect of hyperammonaemia on blood glucose and plasma insulin levels in sheep.

The effects of continuous intravenous infusions (6 h) of ammonium chloride (5.6; 11.2; and 16.8 mumol.kg-1.min) on plasma glucose and immunoreactive insulin (I.R.I.) levels were studied in three adult sheep. Infusions of 5.6 and 11.2 mumol.kg-1.min elevated ammonia levels in circulating blood from 100 to 150 and 300 microgram.100 ml-1, respectively, but showed no appreciable effect on plasma glucose and I.R.I. concentrations. Infusion of 16.8 mumol.kg-1.min-1 resulted in a blood ammonia concentration of about 400 microgram.100 ml-1 after six hours of infusion. Blood ammonia returned to normal 1 to 2 hours after the end of infusion. Plasma glucose concentration tended to increase slightly from 65 to 75 mg . 100 ml-1 when 16.8 mumol of NH4Cl were infused kg-1.min-1 and remained at the elevated level at least for two additional hours when ammonia infusions were stopped. Plasma I.R.I. tended to decrease from 48 to 38 microunits . ml-1 during the time of the NH4Cl infusion and increased continually to 82 microunits . ml-1 when NH4Cl infusions were stopped. It is concluded from the time courses of plasma glucose and plasma I.R.I. that the effect of ammonia infusion of these parameters cannot entirely be explained by a regulatory release of adrenaline.

The dependence of exocrine pancreatic secretion on insulin in sheep.

Exocrine pancreatic secretion, blood insulin, glucose and free fatty acid concentrations were measured on days 1, 4 and 5 of a 5 d experimental period. Sheep were treated with alloxan (day 2) and insulin (day 5). The volume of pancreatic juice decreased markedly in the diabetic state and returned to the initial value after insulin treatment. The daily secretion of lipase and amylase decreased during development of diabetes. Injection of insulin restored the secretion of lipase but not amylase. It is suggested that insulin potentiates the stimulatory action of the vagus nerve on the pancreatic secretion of sheep.

[Effect of volatile fatty acid concentration in the rumen on blood flow in the mesenteric vessels of sheep]. / Wplyw stezenia LKT w przedzoladkach na przeplyw krwi w naczyniach krezkowych u owiec.

The studies were performed on sheep with chronic rumen fistulae and implanted electromagnetic recorders of blood flow in the anterior mesenteric vein and the anterior mesenteric artery. The animals were fed the diet consisting of sugar beet, urea and mineral salts (diet I) or sugar beet and mineral salts (diet II--nitrogen deficient). The diet caused an increase of blood flow in the mesenteric artery and the mesenteric vein: this increase reached the highest level after 2 hours since the application of the diet. There was noted a positive correlation between the changes of blood flow in the mesenteric vessels and the volatile fatty acid concentration in the rumen. The composition of the diet, differing by a protein level, did not influence significantly the differences in blood flow in the mesenteric vessels. It was suggested that an increase of blood flow in the mesenteric vessels was caused by fermentation of carbohydrates in proventriculi, and hence an increased concentration of VFA in the content attaining the duodenum, stimulation of chemoreceptors in the rumen mucosa and increased activity of cholinergic system in internal organs of the abdominal cavity.

Concentration of free amino acids in the blood and liver of cattle, sheep and rabbits.

Concentration of free amino acids in the plasma, erythrocytes and the liver of cattle, sheep and rabbits was different in various species. The differences concerned mainly glutamine, glutamic acid, proline, alanine, glycine. The participation of endogenic amino acids in gluconeogenesis and the nitrogen recycle was discussed considering the characteristics of their metabolism in ruminants.

Urea and glucose formation in ovine liver after ammonia and lactate loading in vivo.

Ammonium chloride (30 mumol/min/kg bw), lactate (50 mumol/min/kg bw) or ammonium chloride plus lactate were infused for two hours into the mesenteric vein of sheep. Blood samples were taken before, during, and two hours after infusion from portal, hepatic and jugular veins for estimation of ammonia, urea, lactate and glucose. Average portal and hepatic blood flow was 59 +/- 35 and 89 +/- 48 ml/min/kg bw respectively without any regular changes when ammonium chloride or lactate alone were administered. The treatment with ammonium chloride increased the hepatic ammonia fixation from 9.1 +/- 2.1 to 25.2 +/- 5.7 mumol/min/kg bw and urea formation from 17.6 +/- 14.2 to 56.4 +/- 43.2 mumol/min/kg bw. The infusion of ammonium chloride alone provoked a peripheral hyperammonaemia and it increased the endogenous sources of ammonia for urea production. Both lactate and ammonia caused an increase of hepatic glucose release. It was suggested that lactate stimulated mainly gluconeogenesis, and ammonium-glucogenolysis. The effect of ammonia in the last reaction as well as an increased net urea formation in the liver, was probably mediated by the hypoinsulinaemia and/or an increase of adrenaline secretion.

The orotic acid concentration in the blood, milk, and urine of dairy cows fed with urea supplemented diet.

The experiment was performed on 4 cows Black and White, 550-650 kg of body weight, before and during 100 days after parturition. Two cows were fed with control and the next two with urea supplemented diet (urea-N constituting about 20% of total N in ration, 13% c.p. in DM). In cows fed with urea supplemented diet the considerable but unequal increase of urinary orotic acid excretion (particularly evident in first 30 days of lactation) was observed. There was however no influence of urea ration on the level of orotic acid in milk. The average orotic acid level in blood plasma (1.14 +/- 0.71 mumol X l-1 and 0.94 +/- 0.22 mumol X l-1 for control and urea fed cow respectively) established 0.01 and 0.001 of the average orotic acid concentration in urine and milk, respectively. Feeding with urea ration did not affect the level of orotic and UMP but increased the uridine concentration in blood plasma. During the parturition the lowest level of orotic acid in blood plasma, milk and urine was observed.

Comparison of metabolic effect of ammonia and adrenaline infusions in sheep.

Intravenous infusions of ammonium chloride (62.3 mumol.kg-1.min-1) for 30 min caused a significant increase in blood glucose, lactate, pyruvate and free fatty acid (FFA) levels. A similar effect was also observed during infusion of adrenaline. Propanolol--a beta-receptor blocking agent--completely prevented the rise of blood pyruvate and lactate after adrenaline when 8.3 microgram.kg-1.min-1 of propranolol were infused, but not after NH4Cl administration. Lipolytic actions of adrenaline were completely prevented but that of NH4Cl was only significantly diminished by blockade of beta-receptors with propranolol. It was concluded that the influence of ammonium ions on blood lactate and pyruvate and FFA was not entirely mediated by adrenaline.

The influence of phentolamine on the hyperglycaemic and lipolytic effects of ammonia in sheep.

Intravenous infusion over 30 min of ammonium chloride [10-1 g/kg b.w.] caused a significant increase of blood glucose and free fatty acids levels, and a similar effect was observed with adrenaline. Phentolamine [1 mg/kg b.w.] abolished the hyperglycaemic action of ammonium chloride but only slightly diminished the lipolytic effect. It is concluded that the ammonium ion influences carbohydrate metabolism chiefly by way of catecholamines and stimulation of alpha-adrenergic receptors, while tissue lipids are mobilized by ammonia by another route, possibley directly.

Rumen degradability of dry matter and crude fibre of irradiated and sodium hydroxide treated straws.

Wheat straw (WS) and triticale straw (TS) were treated with 2- and 4%-NaOH and/or 300- and 600-kGy radiation doses (accelerated electrons) for improvement of the nutritional value of these feeds. Beside the chemical composition of straws, the nylon bag rumen disappearance of dry matter and crude fibre was estimated. NaOH did not influence the chemical composition of straws, while irradiation significantly reduced the level of crude fibre (CF), neutral detergent fibre (NDF) and acid detergent fibre (ADF) proportionally to the dose. The level of nitrogen free extractives (NFE) and alpha-linked glucose polymers pronouncedly increased in the radiated straws. NaOH treatment raised potential rumen degradability of DM and irradiation did so in the case of potential as well as effective degradability. It was not able to prove the summarized influence of both treatments on DM and CF rumen degradability of the straws. The dynamics of the rumen disappearance of DM was different in the straws.

The depressive action of ammonium chloride on the hepatic blood flow in sheep.

Using the 133Xe clearance method it is shown that NH4Cl infusion into the anterior mesenteric vein decreased capillary blood flow in the liver. Phentolamine completely and propranolol partially prevented the depressive action of NH4Cl on hepatic blood flow. NH5Cl infused into the jugular vein provoked a slight increase in the hepatic blood flow. The adrenaline-like action of ammonium ion on the blood circulation in the liver region is discussed.

Exocrine pancreatic function during cold blockade of the vagus in chronic experiments on calves.

Four calves were prepared surgically to investigate the exocrine pancreatic function in chronic experiments. Cooling devices were implanted on both vagi for temporary, reversible, thermal blockade of the conductivity in the nerves. Cooling of the vagi caused significant decreases of volume, total protein content and trypsin activity in pancreatic juice. All of these variables recovered to the control level immediately after the cooling. Results presented indicate an important role of vagally driven information on the exocrine pancreatic secretion in calves.

Effect of intraduodenal HCl and soybean extract on pancreatic juice secretion during atropinization and cold vagal blockade in calves.

In order to elucidate the mechanisms by which intraduodenal hydrochloric acid (HCl) and soybean extract influence exocrine pancreatic secretion in the young ruminant, we conducted experiments repeatedly on six conscious calves with and without blockade of the extrinsic and intrinsic neural pathways. In the absence of blockade, each of the two stimuli increased the juice volume, the HCl effect being far stronger than that of soybean extract. Intrinsic cholinergic blockade by atropinization blocked the stimulatory work of soybean extract on pancreatic secretion and on HCl-stimulated protein but had a weak effect on the amount of juice evoked by HCl. Temporary vagal blockade by chilling virtually abolished the excitatory effects of both soybean extract and HCl. With or without blockade, duodenal HCl resulted in a noteworthy increase in plasmal secretin and a slight increase in cholecystokinin (CCK). With alimentary proteins, acidification of the duodenum was responsible for both the composition and secretion of pancreatic juice in young calves, generally via neural pathways. Atropine-sensitive nerves of the pancreas totally regulate the intestinal phase of pancreatic juice secretion allied with intraduodenal protein, whereas HCl-dependent excitation of the exocrine pancreas takes place partly via atropine-resistant nerves. However, as hardly any pancreatic juice was secreted independently of the vagi, the vagi are deemed to govern all the postprandial regulatory mechanisms of the exocrine pancreas in the young calf.

Influence of feeding regimen and postnatal developmental stages on antibacterial activity of pancreatic juice.

Antibacterial activity of pancreatic juice in the pig (n = 8) was investigated during early postnatal development and in cattle (n = 6) receiving a different feeding regimen. For pancreatic juice collection, a catheter was surgically implanted in the pancreatic duct. Reintroduction of pancreatic juice was achieved through a T-shaped cannula in the duodenum. Pancreatic juice was collected for 30 min in all cases. In piglets, collections were carried out at 2, 5-6, and 7-10 wk of age, and in cattle, after a standard meal, 48 h starvation, and following 24 h intraduodenal glucose infusion. Antibacterial activity was tested on Micrococcus Pyogenes strain ATTC 6538P by disc agar diffusion technique using nonactivated pancreatic juice, before and after heat treatment for 15 min at 65 and 100 degrees C, respectively. Piglets showed a significant rise in antibacterial activity of pancreatic juice after weaning. In cattle, 48 h of starvation resulted in a marked suppression of antibacterial activity. This activity was found to be normal after a standard meal and comparable to that after 24-h intraduodenal glucose infusion. Heating of pancreatic juice to 65 degrees C caused a 35% increase in the antibacterial potency, whereas heating to 100 degrees C completely abolished it. Additionally, dilution of pancreatic juice to 1:10 did not affect antibacterial potency.

Kinetics of pancreatic juice secretion in relation to duodenal migrating myoelectric complex in preruminant and ruminant calves fed twice daily.

Daily secretion of pancreatic juice, including postprandial responses to food, was investigated in two groups of calves: preruminant (fed with liquid food) and ruminant (fed with solid food). Male Friesian calves (1 week old and 6 weeks old) were surgically fitted with a pancreatic duct catheter, duodenal cannula and two duodenal electrodes. Continuous 24 h collections of pancreatic juice and myoelectrical recordings were performed with minimal restraint and disturbance of animals. In both groups of calves clear periodic fluctuations in pancreatic juice secretion (volume, protein output and trypsin activity) coinciding with duodenal migrating myoelectric complexes (MMC) were recorded. Secretion of juice per cycle and per day was greater in ruminant calves, but the frequency and amplitude of cycles were lower in this group. There were no differences between day and night-time preprandial pancreatic cycles and duodenal MMC in preruminant calves, whilst in ruminant calves, evening MMC were longer than morning MMC. The pancreatic cephalic phase (increase of volume flow, protein output and trypsin activity during and just after food intake) was significant only in preruminant calves following morning feeding. Postprandial pancreatic cycles did not differ from preprandial cycles, except the pancreatic cycle (juice volume and trypsin activity) in which food was offered in preruminant calves. No gastric or intestinal phase was observed in either group of calves. In conclusion, biological cycles of the gastrointestinal tract are present in both preruminant and ruminant calves, and these cycles evolve along with the change from liquid to solid food.

Investigations of the influence of the content of plant crude protein in the ration on the utilisation of urea in dairy cattle. 5. 15N-fractions in the blood of lactating cows given 15N-urea intraruminantly.

The incorporation of urea-15N (given as an intraruminal drench or infusion) into plasma urea and protein of dairy cows fed isoenergetic rations with different levels of plant protein (9, 11, 12, 14, 15 and 17% in DM) was investigated. A nonlinear and asymptotic dependence between the plasma concentration of urea and protein level in the ration was stated. The availability of dietary urea-15N for plasma urea for 48 hours after administration was lowest in cows fed with low protein rations (9 and 11% of plant protein). On the contrary the highest incorporation of urea-15N into plasma protein of these animals was observed. The possible explanation of these results is presented.

Cholecystokinin-8 and vasoactive intestinal polypeptide stimulate exocrine pancreatic secretion via duodenally mediated mechanisms in the conscious pig.

The effects of local and peripheral administration of cholecystokinin-8 (CCK-8) and vasoactive intestinal polypeptide (VIP) on basal pancreatic secretion were investigated in conscious pigs. Five pigs (20 +/- 2 kg, mean +/- S.E.M.) were chronically fitted with a T-shaped cannula in the duodenum, and catheters in the pancreatic duct, jugular vein, and right gastroepiploic artery. The arterial catheter was inserted against the bloodstream with its tip opposite the duodenal branch(es) of the right gastroepiploic artery, so that all injected peptides would reach the duodenal arterial circulation excluding the pancreas. Pancreatic secretion during basal conditions (i.e. after an overnight fast) exhibited a characteristic cyclic pattern (cycle duration, 70 +/- 4.2 min). Secretion volume oscillated between 0.2 +/- 0.04 and 4.0 +/- 0.9 ml kg-1 h-1 (P < 0.001), trypsin output between 9.6 +/- 1.9 and 29.1 +/- 4.1 U kg-1 h-1 (P < 0.001) and protein output between 0.36 +/- 0.08 and 9.2 +/- 1.7 mg kg-1 h-1 (P < 0.001). Infusion into the jugular vein for 1 min, during the trough of pancreatic secretion, of either CCK-8 (15 pmol kg-1 min-1) or VIP (7 pmol kg-1 min-1) did not stimulate pancreatic secretion. However, local infusion of an identical dose of CCK-8 or VIP into the duodenal arterial circulation increased the volume, protein output and trypsin output of the pancreatic juice (P < 0.05 to < 0.001). These results indicate that CCK-8 and VIP can stimulate the exocrine pancreas by a duodenally mediated mechanism.