Giant electron-phonon coupling of the breathing plane oxygen phonons in the dynamic stripe phase of [Formula: see text].

Doped antiferromagnets host a vast array of physical properties and learning how to control them is one of the biggest challenges of condensed matter physics. [Formula: see text] (LSNO) is a classic example of such a material. At low temperatures holes introduced via substitution of La by Sr segregate into lines to form boundaries between magnetically ordered domains in the form of stripes. The stripes become dynamic at high temperatures, but LSNO remains insulating presumably because an interplay between magnetic correlations and electron-phonon coupling localizes charge carriers. Magnetic degrees of freedom have been extensively investigated in this system, but phonons are almost completely unexplored. We searched for electron-phonon anomalies in LSNO by inelastic neutron scattering. Giant renormalization of plane Ni-O bond-stretching modes that modulate the volume around Ni appears on entering the dynamic charge stripe phase. Other phonons are a lot less sensitive to stripe melting. Dramatic overdamping of the breathing modes indicates that dynamic stripe phase may host small polarons. We argue that this feature sets electron-phonon coupling in nickelates apart from that in cuprates where breathing phonons are not overdamped and point out remarkable similarities with the colossal magnetoresistance manganites.

Nematic Correlation Length in Iron-Based Superconductors Probed by Inelastic X-Ray Scattering.

Nematicity is ubiquitous in electronic phases of high-T_{c} superconductors, particularly in the Fe-based systems. We used inelastic x-ray scattering to extract the temperature-dependent nematic correlation length ξ from the anomalous softening of acoustic phonon modes in FeSe, underdoped Ba(Fe_{0.97}Co_{0.03})_{2}As_{2}, and optimally doped Ba(Fe_{0.94}Co_{0.06})_{2}As_{2}. In all cases, we find that ξ is well described by a power law (T-T_{0})^{-1/2} extending over a wide temperature range. Combined with the previously reported Curie-Weiss behavior of the nematic susceptibility, these results point to the mean-field character of the nematic transition, which we attribute to a sizable nematoelastic coupling that is likely detrimental to superconductivity.

Systemic, renal, and colonic effects of intravenous and enteral rehydration in horses.

BACKGROUND: Intravenous (IV) and intragastric (IG) administration of fluid therapy are commonly used in equine practice, but there are limited data on the systemic, renal, and enteric effects. HYPOTHESIS: IV fluid administration will increase intestinal and fecal hydration in a rate-dependent manner after hypertonic dehydration, but will be associated with significant urinary water and electrolyte loss. Equivalent volumes of IG plain water will result in comparatively greater intestinal hydration with less renal loss. ANIMALS: Six Thoroughbred geldings. METHODS: Experimental study. 6 by 6 Latin square design investigating constant rate IV administration at 50, 100, and 150 mL/kg/d over 24 hours in horses dehydrated by water deprivation. Equivalent volumes of IG plain water were administered by 4 bolus doses over 24 hours. RESULTS: Water deprivation resulted in a significant decrease in the percentage of fecal water, and increases in serum and urine osmolality. IV fluids administered at 100 and 150 mL/kg/d restored fecal hydration, but increasing the rate from 100 to 150 mL/kg/d did not confer any additional intestinal benefit, but did result in significantly greater urine production and sodium loss. Equivalent 24-hour volumes of plain water resulted in greater intestinal water and less urine output. CONCLUSIONS AND CLINICAL IMPORTANCE: IV polyionic isotonic fluids can be used to hydrate intestinal contents in situations where enteral fluids are impractical. IV fluids administered at three times maintenance are no more efficacious and might be associated with adverse physiological findings after withdrawal. Bolus dosing of IG water can be used to restore intestinal water with minimal adverse effects.

Equine gastrointestinal motility research: where we are and where we need to go.

Equine gastrointestinal motility is a central issue in cases of equine colic, post operative convalescence and alimentary conditions encountered in practice. There are significant syndromes of intestinal dysmotility in the horse such as obstructive disorders and post operative ileus that are still poorly understood. This review describes the various areas of research that aim to elucidate the pathogenesis of intestinal hypo- or hypermotility by research methods, which include studies at the cellular level, and those that employ in vitro or in vivo techniques of evaluating the physiology and mechanical means of ingesta transit through the alimentary tract. The review discusses future directions for studies which will hopefully lead to better understanding and appropriate measures for diagnosis, therapy and prevention of ileus and other motility disorders.

Effect of paddock vs. stall housing on 24 hour gastric pH within the proximal and ventral equine stomach.

REASONS FOR PERFORMING STUDY: Stall housing has been suggested as a risk factor for ulcer development in the equine stomach; however, the exact pathogenesis for this has not been established. OBJECTIVES: To investigate the effect of 3 environmental situations (grass paddock, stall alone or stall with adjacent companion) on pH in the proximal and the ventral stomach. METHODS: Six horses with permanently implanted gastric cannulae were used in a randomised, cross-over, block design. Each horse rotated through each of three 24 h environmental situations. Horses remained on their normal diet (grass hay ad libitum and grain b.i.d.) throughout the study. Intragastric pH was measured continuously for 72 h just inside the lower oesophageal sphincter (proximal stomach) and via a pH probe in the gastric cannula (ventral stomach). RESULTS: Neither proximal nor ventral 24 h gastric pH changed significantly between the 3 environmental situations. Mean hourly proximal gastric pH decreased significantly in the interval from 01.00-09.00 h compared to the interval from 13.00-20.00 h, regardless of environmental situation. Median hourly proximal pH only differed in the interval from 06.00-07.00 h compared to the interval 14.00-19.00 h. Neither mean nor median hourly ventral gastric pH varied significantly with the time of day. CONCLUSIONS: The change in housing status used in the current study did not affect acid exposure within either region of the equine stomach. The pH in the ventral stomach was uniformly stable throughout the study, while the proximal pH demonstrated a 24 h circadian pattern.

Effect of systemic lidocaine on visceral and somatic nociception in conscious horses.

REASONS FOR PERFORMING STUDY: Commonly used analgesics (nonsteroidal anti-inflammatory agents, opioids and alpha2-agonists) have unwanted side effects. An effective alternative with minimal adverse effects would benefit clinical equine pain management. OBJECTIVES: To compare the effect of lidocaine or saline on duodenal and rectal distension threshold pressure and somatic thermal threshold in conscious mature horses. HYPOTHESIS: Systemically administered lidocaine would increase somatic and visceral nociceptive thresholds. METHODS: Lidocaine (2 mg/kg bwt bolus followed by 50 microg/kg bwt/min for 2 h) or saline was administered to 6 horses each carrying a permanently implanted gastric cannula, in a randomised, blinded cross-over design. Thermal threshold was measured using a probe containing a heater element placed over the withers which supplied heat until the horse responded. A barostatically controlled intraduodenal balloon was distended until a discomfort response was obtained. A rectal balloon was inflated until extruded or signs of discomfort noted. RESULTS: Thermal threshold was increased significantly 30 and 90 mins after the start of lidocaine infusion. There was no change in duodenal distension pressure and a small but clinically insignificant change in colorectal distension pressure in the lidocaine group. CONCLUSIONS: At the dose used, systemically administered lidocaine produced thermal antinociception but minimal changes in visceral nociception. POTENTIAL RELEVANCE: At these doses, lidocaine may play a role in somatic analgesia in horses.

Colorectal distention in the horse: visceral sensitivity, rectal compliance and effect of i.v. xylazine or intrarectal lidocaine.

REASONS FOR PERFORMING STUDY: Most current models of visceral sensitivity testing in the horse have required visceral cannulation. Colorectal distention (CRD) is a widely used, noninvasive method for testing in other species and could be adapted for use in horses. OBJECTIVES: To develop a protocol of controlled CRD in the conscious horse and to evaluate the effect of i.v. xylazine or intrarectal lidocaine on CRD threshold and rectal compliance. METHODS: Eight horses were used for baseline studies (3 trials each) and 6 horses to evaluate treatments (4 trials, 2 per treatment). A 45 cm diameter polyvinyl balloon attached to plastic tubing was used for rectal distention following a stepwise barostat-controlled inflation pattern. RESULTS: The procedure was well tolerated by all horses. Mean baseline threshold pressure was 14.17 mmHg. Xylazine i.v. resulted in significantly (P < 0.05) higher mean threshold pressures compared to baseline or rectal lidocaine. Rectal compliance increased following lidocaine treatment relative to baseline or xylazine. CONCLUSIONS: CRD offers a noninvasive method for visceral sensitivity testing in the horse. Xylazine raises CRD threshold, while lidocaine increases rectal compliance. POTENTIAL RELEVANCE: The increased rectal compliance following intrarectal lidocaine administration may explain the benefit of its use to facilitate rectal examination.

Effect of dietary corn oil supplementation on equine gastric fluid acid, sodium, and prostaglandin E2 content before and during pentagastrin infusion.

The effect of corn oil (approximately 60% [wt/vol] linoleic acid) dietary supplementation on various components of equine gastric secretion was studied by use of a repeated-measures experimental design. Four healthy adult ponies were surgically fitted with gastric cannulas. The ponies were then fed a free-choice hay diet for 5 weeks, which was followed by 5 weeks of the same diet supplemented with 45 mL of corn oil daily. Gastric contents were analyzed under basal and pentagastrin-stimulated conditions once weekly during the latter 2 weeks on each diet. Gastric contents were collected at 30-minute intervals, and volume, hydrogen ion concentration, sodium content, and prostaglandin E2 (PGE2) content were measured. Data were analyzed by a linear fixed-effect modeling procedure. During the diet supplemented with corn oil, the ponies had, under basal and pentagastrin-stimulated conditions, significantly decreased acid output and significantly increased PGE2 and sodium outputs compared to those measured before corn oil supplementation. We conclude that corn oil supplementation may be an effective and inexpensive way to increase the protective properties of equine glandular gastric mucosa. This could be particularly helpful in reducing the chances of ulceration associated with nonsteroidal anti-inflammatory drug (NSAID) administration.

Effect of GastroGard and three compounded oral omeprazole preparations on 24 h intragastric pH in gastrically cannulated mature horses.

REASONS FOR PERFORMING STUDY: Ulceration of the squamous gastric mucosa is commonly associated with intensive training programmes in horses, but only one compound ('Gastrogard') has been subjected to controlled scrutiny as to therapeutic efficacy. OBJECTIVES: To compare the gastric acid inhibitory efficacy of one manufactured ('GastroGard') and 3 generic pharmacy-compounded preparations of the proton pump inhibitor omeprazole (OME) in the mature horse. HYPOTHESIS: All OME preparations tested would induce a clinically acceptable effect. METHODS: Six healthy mature gastrically cannulated horses of various breeds, 3 mares and 3 geldings, were used. Each product was administered per os once daily (0730 h) at an equivalent dose of 4 mg OME/kg bwt, in a randomised complete repeated measures design for sequence of individual preparation treatment per horse. There was a minimum of 14 days between treatment regimens. A portable unit that recorded pH continuously was attached to a recording electrode fixed within the gastric lumen via the gastric cannula. Three 24 h recordings were made one day before and during Days 2 and 7 after commencement of a 7 day treatment with each of the 4 individual preparations. The horses were fed as usual throughout the study. RESULTS: Only the GastroGard and one other preparation induced a significant increase over baseline in mean percentage of time that the pH was > 4.0 and mean median intragastric pH, during the first 14 and 12 h post treatment respectively, for both Days 2 and 7 post treatment. Both these products had a vehicle pH > 8.0, in contrast to the 2 less effective products, where the vehicle pH was < 6.0. CONCLUSIONS: OME at 4 mg/kg per os s.i.d. can effectively maintain intragastric pH at an accepted anti-ulcerogenic level for at least 12 h post administration in mature horses. In contrast to GastroGard, it should not be expected that all compounded preparations of OME are equally effective in achieving this performance. It appears that vehicle pH might play an important part in determining preparation efficacy. POTENTIAL RELEVANCE: Optimal timing for daily dosing of athletic horses with an effective OME preparation, in order to suppress gastric squamous ulceration, might be 4-8 h prior to a training session.

Porcine ileitis model induced by TNBS-ethanol instillation.

Nine young pigs were used to evaluate the ability of an trinitrobenzene sulfonic acid-ethanol (TNBS-EtOH) mixture, in varying combinations, to induce ileitis comparable to that caused by intraintestinal instillation in other species. The distal ileum was accessed via laparotomy in anesthetized animals and the TNBS-EtOH was instilled via hypodermic needle. In three pigs in which the instillate was not held within an ileal segment, there were no ileal lesions noted upon necropsy at two weeks after instillation. In all six pigs in which the instillate was confined to a 10-cm length of distal ileum for 10-15 min, there was definite gross and histologic evidence of severe ileitis upon necropsy at one week after instillation. The histopathology was more consistent with Th-1- than Th-2-mediated inflammation.

Intragastric pH in critically ill neonatal foals and the effect of ranitidine.

OBJECTIVE: To characterize intragastric pH profiles in critically ill foals and determine whether administration of ranitidine altered pH profiles. DESIGN: Prospective observational study. ANIMALS: 23 hospitalized neonatal foals < or = 4 days of age. PROCEDURE: Intragastric pH was measured continuously for up to 24 hours by use of an indwelling electrode and continuous data recording system. In 21 foals, ranitidine was administered IV. RESULTS: 10 foals had predominantly or exclusively alkaline profiles, 10 had profiles typical of those reported for healthy foals, with periods of acidity (hourly mean pH < 5.0 at least once), and 3 had atypical profiles with periods of acidity. All 10 foals that had intragastric pH profiles typical of healthy foals survived, whereas only 2 foals with alkaline profiles survived, and none of the foals with atypical profiles survived. The effects of ranitidine administration could not be assessed in 13 foals because of a high baseline intragastric pH. In 7 of the remaining 9, ranitidine administration resulted in an alkalinizing response, but this response was often of blunted duration. Ranitidine administration did not appear to alter the intragastric pH profile in the remaining 2 foals. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggested that hospitalized critically ill foals often have intragastric pH profiles different from those reported for healthy foals and may respond differently to ranitidine administration than do healthy foals. Many critically ill foals have continuously alkaline intragastric pH profiles, questioning the need for prophylactic administration of ranitidine in all critically ill foals.

Effect of pyloric blockade and infusion of histamine or pentagastrin on gastric secretion in horses.

OBJECTIVE: To determine the origin of the nonacid (nonparietal) component of gastric secretions in horses induced by pentagastrin infusion. ANIMALS: 6 horses. PROCEDURE: A Latin square design was used, involving 6 horses, 3 treatments, and 2 duodenal intubation conditions (catheter with balloon to obstruct pylorus [B] or without balloon allowing movement of contents between stomach and duodenum [NB]). Each horse had an indwelling gastric cannula and a catheter positioned in the duodenum. Gastric and duodenal contents were collected during 15-minute periods. Each experiment consisted of serial collection periods: baseline; infusion of pyrilamine maleate (1 mg/kg of body weight, IV); not treated; and IV infusion of saline (0.9% NaCl) solution alone, saline solution containing pentagastrin (6 microg/kg x h), or saline solution containing histamine (30 microg/kg x h). Volume of samples was recorded, and electrolyte concentrations were measured. RESULTS: Pentagastrin and histamine stimulated maximal acid output; however, during NB conditions, pentagastrin-induced concentration of hydrogen ions was significantly less than during histamine or pentagastrin infusions during B conditions. The large volume produced in response to pentagastrin during NB conditions was accompanied by increased sodium ion output that was greater than for pentagastrin during B conditions, but both values were significantly greater than values for histamine during B or NB conditions. CONCLUSIONS AND CLINICAL RELEVANCE: Nonparietal secretions collected during IV infusion of pentagastrin are duodenal in origin. Reflux of duodenal contents into the stomach of horses is enhanced by pentagastrin. Flow of duodenal contents into the stomach could have implications in the pathogenesis of ulcers in horses.

Effect of eltenac in horses with induced endotoxaemia.

Ten horses were used in a crossover study to evaluate the effectiveness of eltenac against endotoxaemia. Eltenac (0.5 mg/kg bwt) or saline control was given i.v. then 15 min later, intravenous infusion of endotoxin was begun and continued for 120 min (total dose 100 ng/kg bwt). Horses were monitored for heart and respiratory rates, pulmonary and carotid arterial pressure and core body temperature. Blood was sampled at intervals for measurement of haematological variables and plasma concentrations of lactate, prostanoid metabolites, tumour necrosis factor (TNF) and stress hormones. In comparison with saline-treatment, use of eltenac significantly protected against endotoxin-induced changes in respiratory rate, core temperature, systemic arterial blood pressure (SAP), pulmonary arterial pressure, PCV, and plasma protein, 6-keto prostaglandin F1 alpha, thromboxane B2, epinephrine, and cortisol concentrations. Despite statistical effect of eltenac on SAP, values in both treatment groups remained well above baseline throughout the evaluation period. Significant protective effect of eltenac was not found for heart rate, white blood cell count, plasma lactate concentration or TNF activity. On the basis of these results, it is expected that use of eltenac will provide clinical benefit in horses with naturally occurring endotoxaemia.

Changes in intrauterine pressure after oxytocin administration in reproductively normal mares and in those with a delay in uterine clearance.

Intrauterine pressure was measured in 4 reproductively normal mares and 4 mares with delay in uterine clearance after administration of oxytocin to determine if intrauterine pressure varied between dosage and group. Changes in intrauterine pressure were measured during estrus, when a follicle was > or =35 mm, using a Millar "Mikro-tip" catheter that had 3 discrete pressure sensors/channels. Mares received 4 different treatments of 10, 5, 2.5 or 0 IU (vehicle) of oxytocin. The protocol for each treatment consisted of a 10-min baseline recording, administration of treatment and measurement of changes in intrauterine pressure for 65 min. After administration of the first two treatments, mares were rested for 2 h and the protocol repeated for the remaining 2 treatments. Changes in intrauterine pressure were measured on a physiograph and stored in a computer. The results were analyzed by 4x4 Latin Square Design analysis of variance (ANOVA) using the GLM procedure of the Statistical Analysis System. The ANOVA detected a main effect of treatment (P<0.01) and mare (nested within group; P<0.01) but no effect of channels, group or treatment-by-group interaction. There was a dose-dependent increase in uterine activity in both normal mares and those with delayed uterine clearance. A dose of 10 IU of oxytocin induced a larger number of uterine contractions (5.67+/-0.06) for a longer time (24.09+/-1.18 min) than the 5 IU (4.16+/-0.06 contractions and 16.31+/-1.18; P<0.01 min) or 2.5 IU dose (4.08+/-0.06 contractions and 17.61+/-1.18 min). The first intrauterine wave occurred most often near the tip of the horn in 10 of 12 recordings in normal mares and in 8 of 12 recordings in mares with delayed uterine clearance. It was then propagated from the middle of the horn to the uterine body just cranial to the cervix. There was no pattern of propagation for subsequent intrauterine pressure waves. We conclude that the difference in spontaneous clearance of the uterus between the 2 groups is not reflected in their response to exogenous oxytocin as determined by changes in intrauterine pressure.

Normal equine gastroduodenal secretion and motility.

This article represents an attempt to provide an overview of the current knowledge of equine gastroduodenal secretory and motor activity, with respect to how these functions are controlled and interact. First, the equine gastric mucosal anatomy is discussed in comparison with other monogastric species, with some attention directed at the large nonglandular portion in relation to its function, or lack thereof. Next, control of gastric acid secretion, as assessed by the collection of gastric contents from a cannula or continuous measurement of their changes in pH, is reviewed, pointing out that there appears to be a relatively unobstructed movement of contents between stomach and duodenum in the horse, which can have a strong influence on pH of the gastric contents in particular. Then, methods of evaluating gastroduodenal motility, including recording of myoelectrical activity and changes in intraluminal pressure, and transit of radiolabelled contents from stomach into duodenum, are discussed. Finally, the apparent influence of the gastroduodenal migrating motility complex (MMC) on the composition of fasting gastric contents is introduced to underscore the observation that reflux of duodenal contents into the stomach is probably a common occurrence in the horse, particularly during periods of MMC-related cessation of antral motility.

Comparison of the antisecretory effects of omeprazole when administered intravenously, as acid-stable granules and as an oral paste in horses.

The antisecretory activity of omeprazole on gastric acid when administered i.v., intragastrically or per os, was evaluated in 2 female and 3 castrated male horses. Each horse had been prepared with a chronic indwelling gastric cannula. A single i.v. administration of omeprazole (1.5 mg/kg bwt) was effective in abolishing basal and pentagastrin (PG)-stimulated acid secretion. Once daily, nasogastric administration of omeprazole in acid-stable granules for 5 days inhibited acid secretion in a dose-dependent manner: 57% (1.5 mg/kg bwt) and 98% (5.0 mg/kg bwt) reduction of PG-stimulated acid secretion. The degree of inhibition was maintained over a 19 day treatment period with once daily dosing. A prototype oral paste formulation containing either acid-stable omeprazole granules or uncoated omeprazole powder was equipotent when compared to a similar dosage of acid-stable omeprazole granules administered by nasogastric tube. A dose-dependent inhibition was seen with the oral paste formulation containing omeprazole powder: 55% (1.5 mg/kg bwt) and 77% (3.0 mg/kg bwt) reduction of PG-stimulated acid secretion after 5 days. Therefore, a paste formulation of omeprazole powder may offer an effective, easily administered, once daily acid inhibitory treatment for gastric ulcer disease in horses.

Effect of omeprazole paste on gastric acid secretion in horses.

In a multicentre trial, 13 cannulated horses were treated orally once daily with a paste that delivered omeprazole at a dose of 4 and 5 mg/kg bwt in a 2-period crossover design to evaluate steady state gastric acid suppression. In each period, basal (unstimulated) and pentagastrin-stimulated gastric output were evaluated at 5-8 h after 5 doses, at 13-16 h after 10 doses, and at 21-24 h after 15 doses. Baseline data for gastric acid secretion were collected once for each horse in the month prior to initiation of omeprazole treatment. The inhibition of gastric acid secretion relative to baseline values, following treatment with omeprazole, were calculated and expressed as per cent. Pharmacokinetic data were also collected in this trial. At 4 mg/kg bwt, the oral paste formulation of omeprazole inhibited both basal and pentagastrin-stimulated gastric acid secretion by 99% at 5-8 h after treatment and by 83% (basal) and 90% (pentagastrin-stimulated) at 21-24 h. Inhibition following the administration of omeprazole at a dose of 5 mg/kg bwt was not significantly greater than when given at 4 mg/kg bwt. The results from this study could possibly lead to the development of an effective and practical antisecretory treatment of ulcer disease in horses.

Histamine-induced gastric acid secretion in horses.

OBJECTIVE: To determine gastric secretory responses in horses treated with histamine and to determine the dose of histamine needed to elicit maximal gastric secretion. ANIMALS: 6 adult horses with an indwelling gastric cannula. PROCEDURE: Gastric contents were collected in 15-minute periods, and volume, pH, hydrogen ion concentration, hydrogen ion output, sodium concentration, and sodium output were determined. Values were determined without any treatment (baseline), after administration of pyrilamine maleate (1 mg/kg of body weight, i.v., given during a 15-minute period), and during 1-hour infusions of histamine at 3 rates (7.5, 15, and 30 microg/kg/h, i.v.). RESULTS: Volume and hydrogen ion concentration of gastric contents and hydrogen ion output were significantly increased, compared with baseline values, during histamine infusion. Mean hydrogen ion concentration and hydrogen ion output were significantly greater during infusion of histamine at a rate of 15 or 30 microg/kg/h than at a rate of 7.5 microg/kg/h. Sodium concentration was significantly decreased, compared with baseline value, during histamine infusion, but sodium output was unchanged. CONCLUSIONS: Histamine at doses of 15 and 30 microg/kg/h, i.v. stimulated maximal gastric secretion in horses. Histamine appeared to induce only parietal secretion. CLINICAL RELEVANCE: This study provides additional information related to equine gastric physiology, which may benefit further understanding of the pathogenesis of peptic ulcer disease.