Secondary transport mechanisms in amino acid fed enhanced biological phosphorus removal.

Enhanced biological phosphorus removal (EBPR) water resource recovery facilities (WRRFs) often fail to meet phosphorus discharge permit limits, indicating a need to improve EBPR to reduce environmental phosphorus discharges. EBPR designs are largely based on the Accumulibacter polyphosphate accumulating organism (PAO) metabolism, while understudied Tetrasphaera PAOs are equally important to EBPR in many facilities worldwide. Anaerobic organic carbon competition is believed to be a key driver of EBPR reliability.

5-Hydroxytryptamine (5-HT) and SK&F 103829 contract canine lower esophageal sphincter smooth muscle by stimulating 5-HT2 receptors.

Addition of 5-HT or SK&F 103829 (2,3,4,5 tetrahydro-8[methyl-sulfonyl]-1 H-3-benzazepin-7-ol hydrobromide) contracts isolated strips of canine lower esophageal sphincter (LES) circular smooth muscle. 5-HT acts directly on the smooth muscle, since pretreatment with the neurotoxin TTX does not inhibit this contraction. Depletion of extracellular calcium or pretreatment with nifedipine inhibited the contraction to both 5-HT and SK&F 103829.

Human lower oesophageal sphincter relaxation is associated with raised cyclic nucleotide content.

Increases in cyclic adenosine monophosphate and cyclic guanosine monophosphate content accompany relaxation of isolated strips of opossum and canine lower oesophageal sphincter muscle. The aim of this investigation was to characterise these responses in isolated muscle from the human lower oesophageal sphincter. Electrical stimulation of enteric neurons produced a frequency dependent relaxation of the human lower oesophageal sphincter that was sensitive to tetrodotoxin.

Dimethylphenylpiperazinium (DMPP)-induced relaxation and elevation of cyclic GMP content in canine lower esophageal sphincter (LES).

Cyclic GMP has been proposed as an intracellular mediator of neuronally-induced relaxation in lower esophageal sphincter (LES) smooth muscle. If cyclic GMP is indeed an intracellular messenger, then agents that activate enteric neurons of the sphincter [e.g.

Cold-restraint stress increases rat fecal pellet output and colonic transit.

Increased fecal pellet output that occurs during cold-restraint stress (CRS) was evaluated systematically. Free-feeding rats, which exhibit a reduced occurrence of gastric ulcers under these conditions, were studied. CRS significantly increased fecal pellet production and fluid content.

Activation of cyclic AMP-dependent protein kinase during canine lower esophageal sphincter relaxation.

In isolated strips of opossum lower esophageal sphincter (LES) smooth muscle, elevation of cyclic AMP (cAMP) content is associated with relaxation. Because the activation state of cyclic nucleotide-dependent protein kinases may be a more sensitive measure of functionally important changes in cyclic nucleotide levels, we examined the ability of several pharmacological agents and electrical stimulation of the enteric neurons to activate cAMP dependent-protein kinase (cA-PK) and to relax isolated strips of LES smooth muscle. Addition of either isoproterenol or SK&F 94120, a selective inhibitor of the low Km cAMP phosphodiesterase to isolated strips of canine LES produced concentration-dependent increases in the activity ratio of cA-PK and concentration-dependent relaxations of canine LES.

Cyclic GMP: a potential mediator of neurally- and drug-induced relaxation of opossum lower esophageal sphincter.

Electrical field stimulation (EFS) of isolated strips of opossum lower esophageal sphincter (LES) produced a relaxation that was accompanied by an elevation of intracellular cyclic GMP content. In order to compare the time dependence of the EFS-induced relaxation with that of the elevation of cyclic GMP, the ability of EFS to produce relaxation and increase cyclic GMP was measured. The results of these experiments showed that cyclic GMP content increased before the onset of relaxation.

Cholecystokinin stimulates neuronal receptors to produce contraction of the canine colon.

The motor effects of cholecystokinin 26-33-amide (CCK octapeptide; CCK-OP) and several purported CCK receptor antagonists on canine colonic circular muscle were determined in pentobarbital anesthetized dogs. Intravenous injections of CCK-OP had no effect on colonic motility at doses that contracted the gallbladder, stomach and duodenum. CCK-OP delivered by intraarterial injection to a small segment of the proximal colon produced a dose related increase in colonic motility with one-half maximum response at 12 ng/Kg and maximum response at 50 ng/Kg.

Effects of KC 2450 on the lower esophageal sphincter in vivo and in vitro.

The effect of KC 2450 (racemic 3,5-cis-3-methylamino-2,3,4,5-tetrahydro-1-benzoxepine-5-ol hydrochloride) on lower esophageal sphincter pressure in pentobarbital-anesthetized dogs was determined and compared to the effect of metoclopramide. The ED20 value (i.e.

Motility abnormality in intestinal atresia.

This study was designed to investigate the motility of the small bowel of the lamb under the conditions of experimental intestinal atresia. Of 26 fetal lambs operated upon (50 to 90 days gestation), 13 came to term. All term lambs exhibited a type 3a atresia.

Functional response to vasoactive intestinal peptide in piebald lethal mice.

Diminished concentrations of the gut neuropeptide, vasoactive intestinal peptide (VIP), have been measured by radioimmunoassay in man and mouse models of Hirschsprung's disease. This in vitro study was designed to ascertain the functional response to VIP in aganglionic colon. Seven piebald lethal (PLM) mice with histologically verified aganglionosis and seven normal littermates (NLM) were sacrificed.

Cyclic nucleotide-dependent protein kinases in the lower esophageal sphincter.

The characteristics and regulation of adenosine 3',5'-cyclic monophosphate (cAMP)-dependent and guanosine 3',5'-cyclic monophosphate (cGMP)-dependent protein kinases (PKs) in opossum, canine, and human lower esophageal sphincter (LES) were investigated. As measured by the incorporation of 32P from [gamma-32P]adenosine 5'-triphosphate (ATP) into histone, LES homogenates from all three species contained three distinct types of PK: cAMP-dependent PK, cGMP-dependent PK, and cyclic nucleotide-independent PK. In all three species, cAMP-dependent PK comprised approximately 80%, cGMP-dependent PK comprised approximately 10%, and cyclic nucleotide-independent PK comprised approximately 10% of the total PK activity in the LES.

Lower esophageal sphincter relaxation is associated with increased cyclic nucleotide content.

Experiments were conducted to determine whether relaxation of the opossum isolated lower esophageal sphincter (LES), induced by electrical field stimulation (EFS) or various pharmacological agents, is associated with changes in cyclic nucleotide content. EFS relaxed the LES in a frequency-dependent manner with 0.7 Hz producing half-maximal relaxation.

DA1 receptor mediates dopamine-induced relaxation of opossum lower esophageal sphincter in vitro.

The objective of the present experiments was to determine the specific receptor subtype through which dopamine (DA) receptor agonists relax the lower esophageal sphincter in vitro. Opossum lower esophageal sphincter smooth muscle strips were placed in oxygenated Krebs' solution containing propranolol and cocaine. The tissues were placed at a tension that gave maximum relaxation to electrical field stimulation and were then pretreated with phenoxybenzamine.

Effect of auranofin (SK&F 39162) on water and electrolyte flux in canine small bowel: a possible diarrheogenic mechanism.

Auranofin (AF) a new antiarthritic gold compound effective when administered orally, frequently causes diarrhea with abnormal stool electrolyte content. Studies were designed to determine the mechanism of the diarrhea caused by AF. In perfused canine Thiry-Vella loops, AF caused significant elevations in effluent volume, osmolarity, and sodium concentration and a significant decrease in potassium concentration.

Effects of calcium channel entry blockers, nifedipine and nilvadipine, on colonic motor activity.

The effects of the dihydropyridine calcium channel entry blockers nifedipine and nilvadipine on colonic contractions were determined in vitro and in vivo. In circular muscle strips prepared from the canine proximal colon, cumulative concentration-response curves were generated to potassium chloride (KCl), acetylcholine (ACh) and substance P, and the effects of electrical field stimulation were determined. Responses to KCl and ACh were examined in circular muscle strips prepared from the monkey proximal and distal colon.

Total intestinal aganglionosis.

Total Intestinal Aganglionosis is a rare, uniformly fatal condition with absence of ganglia from the duodenum to the rectum. A neonate with this extreme form of Hirschsprung's disease is presented with a review of 12 previously reported cases. Smooth muscle strips from this infant's gastrointestinal tract demonstrated viable cholinergic receptors, absence of intrinsic neuronal innervation, and colonic contractile activity to the purported peptidergic neurotransmitter cholecystokinin.

Use of horseradish peroxidase to identify hindbrain sites that influence gastric motility in the cat.

To identify hindbrain sites that influence gastric motility, we administered multiple injections of horseradish peroxidase into the anterior surface of the antrum near the lesser curvature in 3 cats, and used light microscopy to identify horseradish peroxidase-positive neurons in the hindbrain. Retrogradely labeled neurons were found evenly distributed on both sides in the dorsal motor nucleus of the vagus. Labeling extended from 2.

Action of serotonin on the gastrointestinal tract.

Serotonin is localized in the enterochromaffin cells of the gastrointestinal mucosa and within neurons in the enteric nervous system. It can be released into the blood or into the lumen of the gut. Serotonin inhibits gastric acid secretion and may be an endogenous enterogastrone.

Serotonin regulation of the canine migrating motor complex.

A potential role for endogenous serotonin (5-hydroxytryptamine) in the control of the migrating motor complex (MMC) was investigated in 10 conscious dogs. Strain gage force transducers or silver bipolar recording electrodes were sewn along the small intestine to record motor or myoelectrical patterns of activity, respectively. After an 18-hr fast, serotonin stimulated phase II-like circular muscle contractions when administered during phase I of the MMC.

Effects of hindbrain stimulation on lower esophageal sphincter pressure in the cat.

Lower esophageal sphincter (LES) pressure was measured in anesthetized cats during electrical stimulation of the dorsal motor nucleus of the vagus (DMV) and nucleus ambiguus (NA). Stimulation parameters were varied to determine maximal changes in LES pressure and upper gastrointestinal motor responses. LES pressure decreased significantly during DMV and NA stimulation.

Circular esophageal myotomy in the rhesus monkey: anatomical and physiological effects.

Thirty-one rhesus monkeys were divided into six groups: a control group of 4 monkeys in which resection of 33% of the thoracic esophagus with end-to-end anastomosis was performed without myotomy, and test groups of 4 to 6 monkeys each in which circular myotomy in the proximal segment, distal segment, or both was combined with a 25% or 33% resection. In the control group, 2 of 4 monkeys survived. In the test groups, myotomy reduced longitudinal tension by 20 to 58%.

Hindbrain GABA receptors influence parasympathetic outflow to the stomach.

Blockade of gamma-aminobutyric acid receptor function by direct microinjection of bicuculline into the nucleus ambiguous in cats produced a marked increase in gastric motility which was mediated by the vagus nerve. This effect was reversed by muscimol. These data indicate that the nucleus ambiguous may be an important brain site influencing gastric function and that the neurotransmitter controlling parasympathetic overflow from this nucleus to the stomach is gamma-aminobutyric acid.

Gastric and pyloric motor response to sympathetic nerve stimulation after chemical sympathectomy.

This study evaluated the effect of electrical stimulation of the greater splanchnic nerve on gastric and gastroduodenal motility in 6-hydroxydopamine (6-OHDA)-pretreated anesthetized dogs. Biopsies from the stomach, pylorus and duodenum were obtained and analyzed by catecholamine fluorescence microscopy. Degeneration of adrenergic terminals in Auerbach's plexus was complete at 1 week.