Effect of vasoactive intestinal polypeptide on porcine gastrointestinal electrical activity.

The influence of intravenous infusion of VIP, 150 and 300 pmol/kg/min, on gastrointestinal electrical activity was studied in conscious piglets with electrodes implanted in the wall of the antrum pylori, duodenum, jejunum, and ileum. Both doses resulted in a decrease in antral electrical activity. In the small intestine, only the lower dose caused a shortening of the irregular spiking activity phase in the jejunum and ileum. In the jejunum this resulted in a reduction of the MMC interval. It may be concluded that the prevailing effect of VIP is an inhibition of gastrointestinal electrical activity in the piglet.

Effect of the C-terminal tetrapeptide amide of gastrin (CCK-4) and pancreatic polypeptide on gastrointestinal electrical activity in the conscious miniature pig.

The effect of IV infusion of CCK-4, 33.2 and 332 pM/kg/min, and pancreatic polypeptide (PP), 4.8 and 48 pM/kg/min, on gastrointestinal electrical activity was studied in conscious miniature pigs with electrodes implanted in the wall of the antrum pylori and small intestine. In the antrum pylori infusion of the higher dose of both peptides provoked an increase in frequency of the basic electrical rhythm together with a decrease in frequency of spike bursts. In the studied dose range CCK-4 and PP were without influence on small intestinal electrical activity.

Effect of CCK-8 on myoelectrical activity of the gastrointestinal tract in the conscious miniature pig.

In conscious miniature pigs, with implanted electrodes in the wall of the antrum pylori, duodenum, jejunum, and ileum, the influence of IV infusions of CCK-8 (17.5 and 175 pM/kg/min) on gastrointestinal myoelectrical activity was measured. Although both doses under study induced a decrease in antral spike activity. only the higher dose resulted in an overall decrease in integrated myoelectrical activity. In the ileum both doses augmented spiking activity during the infusion, but inhibited electrical activity after the end of the infusion. No response was observed in the duodenum and jejunum. The experiments demonstrate the overall inhibitory effect of CCK-8 on antral electrical activity and its stimulatory influence on ileal smooth muscle.

Effect of infusion of a diarrheogenic dose of PGE2 on gastrointestinal electrical activity in the conscious piglet.

In 5 conscious piglets with electrodes implanted on the antrum pylori and small intestine, phasic and integrated electrical activity was daily recorded. PGE2, 10 micrograms/kg/min, was infused intravenously during 1.5 h and the induced changes in electrical activity were analyzed. Clinical appearance was also studied. PGE2 induced an inhibition in both antral and intestinal activity. In the antrum this inhibition was characterized by a decrease in the frequency of electrical control activity and fast oscillations, and an increase in the duration of the inhibitory phase. Small intestinal recordings revealed an increase in the quiescence phase for the duodenum and a decrease in the integrated total activity for the duodenum, jejunum and ileum, induced by a decrease in phase II activity. PGE2 was without influence on phase III activity and the recycling of the migrating myoelectrical complexes. All piglets developed a severe diarrhea. Vomiting, sedation, fever and shivering were observed in most animals. These data suggest that the diarrheogenic effect of PGE2 is not provoked by an increase in small intestinal motility. Moreover, the direct effect of this PG is a partial inhibition of gastrointestinal electrical activity.

Influence of PGF2 alpha on gastrointestinal activity in the conscious piglet.

In 5 conscious piglets with electrodes implanted on the antrum pylori, duodenum, jejunum and ileum, the effect of intravenous infusion of PGF2 alpha, 1 and 10 micrograms/kg/min during 2 h, on gastrointestinal electrical activity was studied. The influence of the PG, 10(-8) to 10(-4) M, on longitudinal tissue strips from the same segments was also examined. The in vitro results demonstrate that PGF2 alpha has only a weak contractile effect on duodenal and jejunal strips. This effect was enhanced in the presence of atropine and indomethacin. In the in vivo part of the study PGF2 alpha induced an inhibition of antral electrical activity as evidenced by a prolongation of the inhibitory phases and a reduction of the frequency of the fast oscillations. In the small intestine only ileal activity was changed significantly. PGF2 alpha provoked an increase in the phase II or irregular spiking activity and an increase in the interval of the migrating myoelectrical complexes in this segment.

Influence of leukotriene D4 on arterial pressure and gastrointestinal electrical activity in the conscious piglet.

In 6 conscious weaned piglets with implanted electrodes in the corpus and antrum of the stomach, the duodenum, jejunum, ileum and caecum the influence of intravenous infusion of leukotriene (LT)D4, 0.1 and 1 microgram kgmin for 10 min, on mean arterial pressure and gastrointestinal electrical activity was examined. LTD4 induced a significant increase in arterial pressure. Gastrointestinal electrical activity, however, was little influenced, since only the antrum pylori revealed a transient decrease.

Influence of prostaglandin E2 infusion on gastrointestinal electrical activity in the conscious piglet.

In 5 conscious piglets with implanted electrodes in the antrum pylori, duodenum, jejunum and ileum, electromyographic activity was recorded daily on a multichannel recorder with a time constant of 0.03 s for intestinal and of 1 s for gastric recordings, and simultaneously integrated at 20 s intervals. PGE2 was infused for 2 h in relatively low doses of 0.1 and 1 microgram/kg/min, to avoid excessive hypersecretion, which would disguise direct effects. Each dose was tested once in each animal with a 1 week interval. Infusion of 0.1 microgram/kg/min revealed no significant changes in antral and small intestinal electrical activity. One microgram/kg/min however induced a strong depression of fast oscillations until the end of the infusion and prolongation of the inhibitory phase in the antrum following a duodenal phase of regular spiking activity. Intestinal segments displayed a prolongation of the quiescent phase and a decrease in the integrated area curve of the phase of irregular spiking activity. Recurrence of the phase of regular spiking activity was unaltered in either segment. These data suggest that the direct effect of PGE2 on gastrointestinal motility in the piglet is a partial inhibition of intestinal contractions.

Histamine H1- and H2-receptors in the mesenteric vascular bed of the pig.

In order to study whether both histamine H1- and H2-receptors are present in the pig mesenteric vascular bed, natural histamine, 2-(2-pyridyl) ethylamine and 4-methylhistamine, as well as mepyramine and metiamide, were infused directly into the superior mesenteric artery. The results indicate that histamine H1- and H2-receptors, both inducing vasodilation, are present in the mesenteric circulation of the pig. Jejunal motility proved to be influenced by H1-receptor stimulation only.

In vitro adhesion of K88ab-, K88ac- and K88ad-positive Escherichia coli to intestinal villi, to buccal cells and to erythrocytes of weaned piglets.

The phenotype of 21 weaned piglets, concerning adhesion of Escherichia coli possessing K88ab, K88ac or K88ad fimbriae to pig cells, was determined in an in vitro assay. Comparison was made with adhesion of these three K88 variant strains to buccal mucosal epithelial cells and to erythrocytes (haemagglutination) in the same piglets. Whereas adhesion of the three K88 variant strains to intestinal villi was piglet specific, buccal cell adhesion (BCA) and haemagglutination (HA) were not. The K88ab strain was weakly adhesive or non-adhesive in the BCA and negative in the HA test. K88ac strains consistently gave negative and K88ad consistently gave positive results in both assays. After washing the bacteria with phosphate-buffered saline, the K88ab strain revealed a positive HA test. Neither the BCA, nor HA test can be used to determine the pig intestinal adhesive phenotype.

Comparison of the in vitro adhesion of K88, K99, F41 and P987 positive Escherichia coli to intestinal villi of 4- to 5-week-old pigs.

The adhesion of K88ab, K88ac, K88ad, P987, K99, F41 and K99/F41 positive Escherichia coli strains to duodenal, jejunal and ileal villi was studied using an in vitro adhesion assay. The villi were harvested from 4- to 5-week-old pigs. The K88+ strains adhered in large numbers (42 +/- 5 to 81 +/- 4 E. coli/250 microns villous length) to the villi from most pigs and in low to moderate numbers (5 +/- 2 to 24 +/- 7 E. coli/250 microns villous length) or not to villi of some pigs. The K99+ and F41+ strains either adhered in low numbers (1 +/- 1 to 11 +/- 2 E. coli/250 microns villous length) or did not adhere, whereas the P987+ and K99/F41+ strains always adhered in low to moderate numbers (2 +/- 1 to 26 +/- 2 E. coli/250 microns villous length). The number of bacteria adhering to the villi was the highest for the K88ab+ and K88ac+ strains (55 +/- 5 to 81 +/- 4 E. coli/250 microns villous length) and decreasing in the following order: K88ad > P987 > K99/F41 > K99 > F41 (= 1 +/- 1 to 4 +/- 1 E. coli/250 microns villous length). There was no difference in the adhesion of the villi of the different small intestinal segments for the P987+ and F41+ strains. The K99+ strains adhered significantly more to the villi of the caudal half of the small intestine, the K99/F41+ strain to jejunal and ileal and the K88+ strains to jejunal villi in comparison to duodenal ones.

Effect of experimentally-induced villus atrophy on adhesion of K88ac-positive Escherichia coli in just-weaned piglets.

Three- to four-week-old, just-weaned piglets were infected with transmissible gastroenteritis (TGE) virus and the next day with K88ac+ enterotoxigenic Escherichia coli (ETEC). Histological examination of caudal jejunum and ileum of piglets killed 2-3 days after virus challenge (1-2 days after ETEC infection) revealed severe villus atrophy especially in the jejunum compared with controls (P less than 0.05). Four-5 days after TGE virus infection villus length increased and after 7 days it was near normal. Villi scraped from jejunal and ileal mucosa of the piglets were incubated in vitro with K88ac+ E. coli and the number of bacteria adhering to 250 micron villus brush border was counted. Attachment of bacteria to villi of piglets killed 2-3 days after TGE virus infection was significantly decreased in comparison with adhesion to villi of non-infected piglets or of piglets killed 7 days after the virus infection. Correlation between in vitro adhesion and villus height was 0.6649 (P less than 0.001). The results suggest that the experimentally-induced villus atrophy was attended with a temporarily diminished susceptibility of villus enterocytes to adhesion of K88ac+ E. coli.

[Animal experiments: legal, scientific and ethical aspects]. / Dierexperimenten: wettelijke, wetenschappelijke en ethische aspecten.

Among the legal aspects the following topics are treated: the definitions of an experimental animal, an animal experiment and alternative methods with special reference to the 3 R's (replacement, reduction and refinement of animal experiments); the qualifications, education and training of researchers and animal technicians; the licence for animal experimentation; the control on animal welfare; the origin and identification of experimental animals; statistical data on the number of experimental animals; ethics committees and their structure and functions in The Netherlands and Flanders. Extrapolation, species specificity and variability are the most important scientific limitations of animal experimentation. After a short historical survey on the man-animal relation, the following ethical aspects are discussed: the instrumental versus intrinsic value of an experimental animal; the hybrid status of the animal; the objectives of animal rights movements; the balance between the human benefit of an animal experiment and the discomfort for the animal; the problem of animal rights and animal suffering and pain.

[Effects of prostaglandins, leukotrienes, VIP, carbachol and isopropylnoradrenaline on uterine and vaginal motility in the chicken]. / Inloed van prostaglandines, leukotrienen, VIP, carbachol en isopropylnoradrenaline op de motiliteit van uterus en vagina bij de kip.

In laying hens the influence of prostaglandins (PG's), leukotrienes (LT's), VIP, carbachol and isoproterenol (IPN) on uterine and vaginal motility has been studied, using the techniques of the isolated organ-bath, of the intraluminal pressure registration in the anesthetized hen and of the electromyography in the conscious, non-sedated animal. The PG's, LT's and carbachol induced an activation and IPN a relaxation of isolated uterine strips. Vaginal strips were stimulated by PGF2 alpha and high concentrations of LT's, and relaxed by PGE2, low concentrations of LT's and carbachol. Intravenous injection of PGF2 alpha and LTC4 resulted in an increase in uterine and vaginal pressure, whereas injection of PGE2 induced a pressure increase or decrease in the uterus and a pressure decrease in the vagina. Intravenous infusion of PGE2 provoked an increase in uterine electrical activity and a decrease in vaginal activity. An increase in frequency of bursts of spike potentials in the uterus together with an inhibition of vaginal electrical activity were observed following intravenous injection of LTD4. VIP-infusion resulted in an inhibition of electrical activity of uterus and vagina. Carbachol-infusion stimulated the electrical activity of both oviduct segments, whereas IPN inhibited this activity.

Endotoxic shock in the awake young pig: absence of beneficial effect of prednisolone sodium succinate treatment.

In nonanesthetized young pigs, the influence of prednisolone sodium succinate therapy on a 65% lethal dose of Escherichia coli endotoxin was studied by evaluating clinical signs, several hemodynamic variables, survival rate, and changes seen at necropsy. Endotoxin infusion induced reproducible clinical signs characterized by nausea, vomiting, dyspnea, cyanosis, and moderate excitement followed by severe CNS depression. Among the hemodynamic variables, there were decreases in arterial blood pressure and cardiac output and increases in pulmonary arterial pressure, heart rate, and total peripheral and pulmonary vascular resistances. Core temperature and arterial pH did not change significantly. Survival rate at 30 hours after the start of the endotoxin infusion was 35%. According to the necropsy, marked edema and hemorrhages were in several organs. Treating the experimental animals with prednisolone sodium succinate (3 injections of 10 mg/kg of body weight after the start of the endotoxin infusion) did not influence any of the monitored hemodynamic variables, except for arterial blood pressure, which was higher at the end of the hemodynamic recording period (270 minutes after the start of the endotoxin infusion). Clinical signs, survival rate, and changes at necropsy were similar in both treated and nontreated pigs. This lack of effect can be due to an inappropriate dosage of the steroid or failure of steroid treatment to alleviate endotoxin-mediated effects.

Endotoxin shock in the pig: beneficial effects of pretreatment with prednisolone sodium succinate.

In anesthetized pigs, the influence on cardiovascular performance and on survival rate of IV administration of a large dose of endotoxin (0.5 mg/kg of body weight) was examined. This dose of endotoxin (LD100) resulted in a progressively evolving deterioration of cardiovascular functions and in the death of all animals within 210 minutes (mean +/- SEM: 107 +/- 13 minutes) after it was given. The IV injection of prednisolone sodium succinate, 10 mg/kg at 25 minutes before dosing the pigs with endotoxin resulted in a significant increase in survival time. This effect of the glycocorticoid can only partly be ascribed to an amelioration of the cardiovascular dysfunctions.

Myoelectrical activity changes in the uterus and vagina during oviposition in the conscious domestic hen.

In the unrestrained domestic hen, myoelectrical activity of the uterus and vagina was recorded during the period from 10 min before to 10 min after oviposition. Recordings revealed significant changes in frequency and duration of bursts of spike potentials (BSP) between 3 min before and 2 min after the expulsion of the egg. These changes occurred successively, first in the uterus, then in the vagina. For the uterus, the frequency of BSP per minute increased. However, the duration decreased significantly during the same time period, remaining at the attained activity level throughout the 10-min postoviposition period. In the vagina, changes in BSP were transient. The duration of BSP was sharply augmented prior to oviposition, reflecting a nearly continuous discharge of spike potentials. The frequency reached minimal values after oviposition. The onset of changes in myoelectrical activity may reflect the moment the egg passes the registration electrodes. The increase in frequency of spike potentials may indicate augmented resistance to the passage of the egg in cranial direction (ovarium) so that it is propulsed towards the cloaca. The characteristic pattern of vaginal myoelectrical activity about oviposition argues for the active participation of this oviductal segment in the process.

Influence of prostaglandin E2 on myoelectrical activity of the uterus and vagina in the domestic hen.

In conscious hens, the effect of intra-aortic infusion of prostaglandin E2 (PGE2) on myoelectrical activity of the uterus, utero-vaginal junction (UVJ), vagina, duodenum, and on heart rate was studied. Infusion of .3 micrograms PGE2/animal/min resulted in no significant changes in oviduct activity, whereas 3 micrograms/animal/min induced a significant decrease in vaginal activity but had no significant effect on activity of the uterus and UVJ. Infusion of both doses provoked a decrease in duodenal activity (P less than .05) and an increase in heart rate (P less than .05).

Escherichia coli sepsis and endotoxemia in conscious young pigs.

In conscious pigs the influence of intravenous infusion of live E. coli (7 x 10(8)/kg), of the equivalent amount of endotoxin (20 micrograms/kg) or of a high dose of endotoxin (2.5 mg/kg) on the hemodynamic, clinical and pathological parameters and on survival rate was studied. E. coli and endotoxin infusion resulted in pulmonary hypertension, systemic arterial hypotension, a decrease in cardiac output and an increase in heart rate. Clinical signs were characterized by respiratory and nervous disturbances, whereas necropsy revealed hemorrhages and edema in several organs. Although these findings were similar in the three groups, a marked difference in lethality was observed. Infusion of E. coli or of the high dose of endotoxin resulted in a significant mortality, whereas all pigs survived the infusion of the low dose of endotoxin. This suggests that the lethal pathophysiological mechanisms may only become activated when a sufficient amount of endotoxin is released into the circulation.

Pathophysiology of diarrhoea induced by a combined infection with transmissible gastroenteritis virus and enterotoxigenic Escherichia coli in newly-weaned piglets and the effect of flurbiprofen treatment.

In newly-weaned 3-4 week old piglets (n = 29) diarrhoea (100%) and vomiting (65%) were induced by inoculation with transmissible gastroenteritis virus and enterotoxigenic E. coli strains (0(149):K91:K88ac; LT, STa and STb enterotoxin positive). This combined infection resulted in pronounced mortality within 7 days. During this period the piglets had decreases in body weight, arterial pressure and leucocyte count and increases in heart rate and in total plasma protein concentration. The plasma pH and lactic acid concentration decreased, whereas the values for pO2, pCO2 and frequency of respiration did not change significantly. No significant changes in the serum concentrations of potassium, chloride or calcium were observed, whereas sodium concentration revealed a transient increase. In shocked and dying piglets an increase in haematocrit was observed, whereas base excess and bicarbonate concentration decreased. Flurbiprofen, a potent non-steroidal anti-inflammatory drug, administered intramuscularly on 3 successive days following the combined infection at a dosage of 1 mg/kg/12 h was without beneficial effect on diarrhoea or mortality.

Effect of antisecretory drugs on experimentally induced weanling diarrhoea in piglets.

In 45 newly-weaned 3 to 4-week-old piglets, diarrhoea was induced by a combined infection with transmissible gastroenteritis (TGE) virus and enterotoxigenic E. coli (ETEC) strains. In untreated control animals this dual inoculation resulted in profuse diarrhoea, vomiting, hypovolaemic shock and death of 77% of the animals within five days of TGE virus inoculation. Antisecretory drugs were administered intramuscularly for three consecutive days after experimental infection. The neurolepticum chlorpromazine, at 2 mg/kg/24 h, resulted in a significant inhibition of diarrhoea and vomiting, and in an increase in weight gain and survival. Sedation and hypothermia, however, were serious side-effects. The alpha 2 agonist clonidine, at 80 micrograms/kg/12 h, induced a significant antidiarrhoeal effect and a reduction in mortality. The drug, however, provoked decreased activity of alpha 2-adrenergic excitation and incoordination. The beta-adrenergic antagonist propranolol, at 0.33 mg/kg/8 h, and the calcium channel blocker verapamil, at 2 mg/kg/8 h, had no beneficial effect on the experimentally induced diarrhoea.