Studies in vivo and in vitro on effects of PGE2 on colonic motility in rabbits

1992 ◽  
Vol 262 (1) ◽  
pp. G23-G29 ◽  
Author(s):  
R. Burakoff ◽  
W. H. Percy
Keyword(s):  
Colonic Motility ◽  
Circular Muscle ◽  
Distal Colon ◽  
Muscle Layer ◽  
Distal Region ◽  
Mechanical Activity ◽  
Experimental Conditions ◽  
Motor Effects

Prostaglandins (PG) of the E series are synthesized throughout the gastrointestinal tract, and their elevated levels have been reported in many diarrheal states, including inflammatory bowel disease. It is already known that PGE2 has region-specific and muscle layer-specific effects in different areas of the intestine. The aim of this study was to evaluate possible dose-related motor effects of PGE2 on rabbit proximal and distal colon both in vivo and in vitro. We found that, in the proximal colon in vivo, PGE2 caused inhibition of myoelectric and mechanical activity at low doses but at higher doses caused marked excitation. Under the same experimental conditions, PGE2 caused only excitation in the distal colon, a phenomenon associated with an increase in antegrade contractions and diarrhea. In vitro, PGE2 caused excitation of both proximal and distal colonic longitudinal muscle and relaxation of the circular muscle. Its actions, however, were much more pronounced in the distal region. It is concluded that PGE2 has profound effects on colonic motility that are concentration dependent and that differ with the region of the colon under study. Furthermore, the evidence also suggests that elevated PGE2 levels in disease states may play a significant role in abnormal colonic motility and may facilitate the onset of diarrhea.

Leukotriene D4 excitation of rabbit distal colon arises in the region of the muscularis mucosae

1990 ◽  
Vol 259 (5) ◽  
pp. G753-G759
Author(s):  
W. H. Percy ◽  
S. Y. Lee ◽  
M. B. Burton ◽  
T. Tolentino ◽  
R. Burakoff
Keyword(s):  
Muscularis Propria ◽  
Circular Muscle ◽  
Distal Colon ◽  
Muscle Layer ◽  
Mechanical Activity ◽  
Muscularis Mucosae ◽  
Leukotriene D4 ◽  
In Vitro Techniques

We previously have demonstrated in vivo that intra-arterial administration of leukotriene D4 (LTD4) causes increased myoelectric and mechanical activity in the rabbit distal colon. The aim of this study was to use both in vivo and in vitro techniques to try to elucidate the mechanism underlying this effect. In vivo the excitatory response of the rabbit distal colon to LTD4 was abolished by pretreatment with atropine (0.1 mg/kg iv) or hexamethonium (5 mg/kg iv) or the LTD4 receptor antagonist SK&F 102922 (0.8 micrograms/kg ia). In vitro neither the longitudinal nor the circular muscle layer responded to LTD4 (10(-10) to 10(-7) M) with a contractile response. Over the same concentration range, LTD4 caused contractions of the muscularis mucosae that were attenuated by either SK&F 102922 (10(-9) to 10(-7) M) or indomethacin (10(-6) M) but were unaffected by atropine (10(-6) M), pyrilamine (10(-6) M), or tetrodotoxin (10(-6) M). Full thickness segments of longitudinal muscle, circular muscle, and muscularis mucosae did not contract to LTD4. These data imply that LTD4-induced excitation of the rabbit distal colon in vivo arises as a result of the excitation of LTD4 receptors in the region of the muscularis mucosae and that this leads ultimately to the release of acetylcholine onto the muscularis propria. It is proposed that one possible mechanism leading to the latter effect is an increased excitability of intrinsic nerves resulting from a prostaglandin-induced depression of norepinephrine release from nerves impinging on the submucosal plexus.

Comparison of the effects of leukotrienes B4 and D4 on distal colonic motility in the rabbit in vivo

1989 ◽  
Vol 257 (6) ◽  
pp. G860-G864 ◽  
Author(s):  
R. Burakoff ◽  
E. Nastos ◽  
S. Won ◽  
W. H. Percy
Keyword(s):  
Contractile Activity ◽  
Colonic Motility ◽  
Distal Colon ◽  
Mechanical Activity ◽  
Excitatory Action ◽  
Potential Frequency ◽  
Small And Large Intestine ◽  
Related Increase

Leukotrienes (LTs) have been shown to contract smooth muscle of the small and large intestine in vitro, and an increased mucosal synthesis of leukotrienes has been reported to occur in ulcerative colitis. The purpose of this study was to evaluate the effects of LTs B4 and D4 on the myoelectric and mechanical activity of the rabbit distal colon in vivo and to determine how these effects were modified by indomethacin. LTB4 had a weak excitatory action on both electrical and mechanical activity but this was not statistically significant; LTD4 on the other hand caused a significant dose-related increase in spike potential frequency and contractile activity. Indomethacin alone (1 mg/kg) had no significant effect on the electrical or mechanical activity of the colon but blocked the effects of subsequently administered LTD4. It is concluded from these data that at least part of the excitatory action of LTD4 results from its causing the synthesis and release of excitatory prostaglandins. However, whereas leukotrienes have the potential to play an important role in modulating colonic motility, it seems most likely that this effect would occur after pathological stimulus rather than in the normal healthy colon.

Myogenic mechanism for peristalsis in the cat esophagus

1999 ◽  
Vol 277 (2) ◽  
pp. G306-G313 ◽  
Author(s):  
Harold G. Preiksaitis ◽  
Nicholas E. Diamant
Keyword(s):  
Muscle Contraction ◽  
Slow Wave ◽  
Circular Muscle ◽  
Smooth Muscle Contraction ◽  
Slow Waves ◽  
Mechanical Activity ◽  
Control Mechanisms ◽  
Slow Wave Oscillations

A myogenic control system (MCS) is a fundamental determinant of peristalsis in the stomach, small bowel, and colon. In the esophagus, attention has focused on neuronal control, the potential for a MCS receiving less attention. The myogenic properties of the cat esophagus were studied in vitro with and without nerves blocked by 1 μM TTX. Muscle contraction was recorded, while electrical activity was monitored by suction electrodes. Spontaneous, nonperistaltic, electrical, and mechanical activity was seen in the longitudinal muscle and persisted after TTX. Spontaneous circular muscle activity was minimal, and peristalsis was not observed without pharmacological activation. Direct electrical stimulation (ES) in the presence of bethanechol or tetraethylammonium chloride (TEA) produced slow-wave oscillations and spike potentials accompanying smooth muscle contraction that progressed along the esophagus. Increased concentrations of either drug in the presence of TTX produced slow waves and spike discharges, accompanied by peristalsis in 5 of 8 TEA- and 2 of 11 bethanechol-stimulated preparations without ES. Depolarization of the muscle by increasing K+ concentration also produced slow waves but no peristalsis. We conclude that the MCS in the esophagus requires specific activation and is manifest by slow-wave oscillations of the membrane potential, which appear to be necessary, but are not sufficient for myogenic peristalsis. In vivo, additional control mechanisms are likely supplied by nerves.

In vitro model of acute esophagitis in the cat

2005 ◽  
Vol 289 (5) ◽  
pp. G860-G869 ◽  
Author(s):  
Ling Cheng ◽  
Weibiao Cao ◽  
Claudio Fiocchi ◽  
Jose Behar ◽  
Piero Biancani ◽  
...  
Keyword(s):  
In Vitro Model ◽  
Circular Muscle ◽  
Muscle Layer ◽  
Normal Mucosa ◽  
Esophageal Mucosa ◽  
Acute Esophagitis ◽  
Vitro Model ◽  
Esophageal Contraction

We have shown that IL-1β and IL-6, possibly originating from the mucosa in response to injury, inhibit neurally mediated contraction of esophageal circular muscle but do not affect ACh-induced contraction, reproducing the effect of experimental esophagitis on esophageal contraction. To examine the interaction of mucosa and circular muscle in inflammation, we examined the effect of HCl on in vitro esophageal mucosa and circular muscle. Circular muscle strips, when directly exposed to HCl, contracted normally. However, when circular muscle strips were exposed to supernatants of mucosa incubated in HCl (2–3 h, pH 5.8), contraction decreased, and the inhibition was partially reversed by an IL-6 antibody. Supernatants from the mucosa of animals with in vivo-induced acute esophagitis (AE) similarly reduced contraction. IL-6 levels were higher in mucosal tissue from AE animals than in control mucosa and in AE mucosa supernatants than in normal mucosa supernatants. IL-6 levels increased significantly in normal mucosa and supernatants in response to HCl, suggesting increased production and release of IL-6 by the mucosa. IL-6 increased H2O2 levels in the circular muscle layer but not in mucosa. Exposure of the mucosa to HCl caused IL-1β to increase only in the mucosa and not in the supernatant. These data suggest that HCl-induced damage occurs first in the mucosa, leading to the production of IL-1β and IL-6 but not H2O2. IL-1β appears to remain in the mucosa. In contrast, IL-6 is produced and released by the mucosa, eventually resulting in the production of H2O2 by the circular muscle, with this affecting circular muscle contraction.

Neural control of canine colon motor function: studies in vitro

1988 ◽  
Vol 66 (3) ◽  
pp. 359-368 ◽  
Author(s):  
T. Gonda ◽  
E. E. Daniel ◽  
F. Kostolanska ◽  
M. Oki ◽  
J. E. T. Fox
Keyword(s):  
Substance P ◽  
Neural Control ◽  
Circular Muscle ◽  
Distal Colon ◽  
Field Stimulation ◽  
Inhibitory Effects ◽  
Release Of Acetylcholine ◽  
Neural Excitation

The responses of strips of the canine colon to stimulation of intrinsic nerves and to the probable mediators of these nerves were studied in vitro. Studies were carried out using longitudinal and circular muscle strips from proximal and distal colon with field stimulation and addition of agents to the bath. Overall, these and other studies in vivo suggested that acetylcholine was an ubiquitous mediator of neural excitation. Norepinephrine had mixed inhibitory and excitatory effects, the latter only in circular muscle. Inhibitory effects of norepinephrine seemed to be both pre- and post-synaptic but no evidence that it was released by field stimulation was obtained. Substance P had excitatory effects chiefly by release of acetylcholine. It, in addition to norepinephrine, at least in circular muscle, deserves evaluation as the mediator of noncholinergic excitation to high frequency field stimulation. Although vasoactive intestinal peptide sometimes had inhibitory effects, these were incomplete and inconsistent. However, further evaluation of its possible role as a nonadrenergic, noncholinergic inhibitory mediator is required to determine if it is involved as one component in the response. Few qualitative differences existed between responses of various regions of the colon to potential neuromediators, although there were some consistent differences between responses of longitudinal and circular muscle. Some differences existed in responses obtained earlier in vivo and in vitro. In particular, inhibitory effects following excitation by substance P on field stimulation were found only in vivo. Nonadrenergic, noncholinergic inhibitory responses to field stimulation were consistently present only in vitro. These differences have not been explained.

Neuronal Inhibition Determines the Gastrointestinal Motor State

Physiology ◽  
1996 ◽  
Vol 11 (2) ◽  
pp. 67-71 ◽  
Author(s):  
DS Delbro
Keyword(s):  
Contractile Activity ◽  
Circular Muscle ◽  
Muscle Layer ◽  
Blocking Agent ◽  
Myenteric Neurons ◽  
Circular Muscle Layer ◽  
Neuronal Inhibition ◽  
Gastrointestinal Motor

The nerve-blocking agent tetrodotoxin induces contractile activity of the gut circular muscle, in vitro, and intestinal hypermotility, in vivo. According to an hypothesis put forward more than 20 years ago, the circular muscle layer is tonically suppressed due to spontaneously active myenteric neurons that "drive" inhibitory motoneurons to the muscle.

Superoxide, Xanthine Oxidase and Platelet Reactions: Further Studies on Mechanisms by which Oxidants Influence Platelets

1981 ◽  
Vol 45 (03) ◽  
pp. 290-293 ◽  
Author(s):  
Peter H Levine ◽  
Danielle G Sladdin ◽  
Norman I Krinsky
Keyword(s):  
Superoxide Dismutase ◽  
Cytochrome C ◽  
Xanthine Oxidase ◽  
Direct Effect ◽  
Platelet Function ◽  
Experimental Conditions ◽  
Release Reaction

SummaryIn the course of studying the effects on platelets of the oxidant species superoxide (O- 2), Of was generated by the interaction of xanthine oxidase plus xanthine. Surprisingly, gel-filtered platelets, when exposed to xanthine oxidase in the absence of xanthine substrate, were found to generate superoxide (O- 2), as determined by the reduction of added cytochrome c and by the inhibition of this reduction in the presence of superoxide dismutase.In addition to generating Of, the xanthine oxidase-treated platelets display both aggregation and evidence of the release reaction. This xanthine oxidase induced aggreagtion is not inhibited by the addition of either superoxide dismutase or cytochrome c, suggesting that it is due to either a further metabolite of O- 2, or that O- 2 itself exerts no important direct effect on platelet function under these experimental conditions. The ability of Of to modulate platelet reactions in vivo or in vitro remains in doubt, and xanthine oxidase is an unsuitable source of O- 2 in platelet studies because of its own effects on platelets.

Desmopressin (DDAVP) Enhances Platelet Adhesion to the Extracellular Matrix of Cultured Human Endothelial Cells through Increased Expression of Tissue Factor

1997 ◽  
Vol 77 (05) ◽  
pp. 0975-0980 ◽  
Author(s):  
Angel Gálvez ◽  
Goretti Gómez-Ortiz ◽  
Maribel Díaz-Ricart ◽  
Ginés Escolar ◽  
Rogelio González-Sarmiento ◽  
...  
Keyword(s):  
Extracellular Matrix ◽  
Endothelial Cells ◽  
Tissue Factor ◽  
Platelet Adhesion ◽  
Umbilical Vein ◽  
Procoagulant Activity ◽  
Experimental Conditions ◽  
Chromogenic Assay

SummaryThe effect of desmopressin (DDAVP) on thrombogenicity, expression of tissue factor and procoagulant activity (PCA) of extracellular matrix (ECM) generated by human umbilical vein endothelial cells cultures (HUVEC), was studied under different experimental conditions. HUVEC were incubated with DDAVP (1, 5 and 30 ng/ml) and then detached from their ECM. The reactivity towards platelets of this ECM was tested in a perfusion system. Coverslips covered with DD A VP-treated ECMs were inserted in a parallel-plate chamber and exposed to normal blood anticoagulated with low molecular weight heparin (Fragmin®, 20 U/ml). Perfusions were run for 5 min at a shear rate of 800 s1. Deposition of platelets on ECMs was significantly increased with respect to control ECMs when DDAVP was used at 5 and 30 ng/ml (p <0.05 and p <0.01 respectively). The increase in platelet deposition was prevented by incubation of ECMs with an antibody against human tissue factor prior to perfusion. Immunofluorescence studies positively detected tissue factor antigen on DDAVP derived ECMs. A chromogenic assay performed under standardized conditions revealed a statistically significant increase in the procoagulant activity of the ECMs produced by ECs incubated with 30 ng/ml DDAVP (p <0.01 vs. control samples). Northern blot analysis revealed increased levels of tissue factor mRNA in extracts from ECs exposed to DDAVP. Our data indicate that DDAVP in vitro enhances platelet adhesion to the ECMs through increased expression of tissue factor. A similar increase in the expression of tissue factor might contribute to the in vivo hemostatic effect of DDAVP.

Applicability of Instability Index for In vitro Protein Stability Prediction

2019 ◽  
Vol 26 (5) ◽  
pp. 339-347 ◽  
Author(s):  
Dilani G. Gamage ◽  
Ajith Gunaratne ◽  
Gopal R. Periyannan ◽  
Timothy G. Russell
Keyword(s):  
Protein Stability ◽  
Caulobacter Crescentus ◽  
Effect Of Temperature ◽  
Instability Index ◽  
Dipeptide Composition ◽  
Experimental Conditions ◽  
The Stability ◽  
Vitro Protein

Background: The dipeptide composition-based Instability Index (II) is one of the protein primary structure-dependent methods available for in vivo protein stability predictions. As per this method, proteins with II value below 40 are stable proteins. Intracellular protein stability principles guided the original development of the II method. However, the use of the II method for in vitro protein stability predictions raises questions about the validity of applying the II method under experimental conditions that are different from the in vivo setting. Objective: The aim of this study is to experimentally test the validity of the use of II as an in vitro protein stability predictor. Methods: A representative protein CCM (CCM - Caulobacter crescentus metalloprotein) that rapidly degrades under in vitro conditions was used to probe the dipeptide sequence-dependent degradation properties of CCM by generating CCM mutants to represent stable and unstable II values. A comparative degradation analysis was carried out under in vitro conditions using wildtype CCM, CCM mutants and two other candidate proteins: metallo-β-lactamase L1 and α -S1- casein representing stable, borderline stable/unstable, and unstable proteins as per the II predictions. The effect of temperature and a protein stabilizing agent on CCM degradation was also tested. Results: Data support the dipeptide composition-dependent protein stability/instability in wt-CCM and mutants as predicted by the II method under in vitro conditions. However, the II failed to accurately represent the stability of other tested proteins. Data indicate the influence of protein environmental factors on the autoproteolysis of proteins. Conclusion: Broader application of the II method for the prediction of protein stability under in vitro conditions is questionable as the stability of the protein may be dependent not only on the intrinsic nature of the protein but also on the conditions of the protein milieu.

scholarly journals Non-invasive skin sampling of tryptophan/kynurenine ratio in vitro towards a skin cancer biomarker

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Skaidre Jankovskaja ◽  
Johan Engblom ◽  
Melinda Rezeli ◽  
György Marko-Varga ◽  
Tautgirdas Ruzgas ◽  
...  
Keyword(s):  
Skin Cancer ◽  
Relative Increase ◽  
Cancer Biomarker ◽  
Cancer Diagnostics ◽  
Sampling Time ◽  
Skin Permeability ◽  
Experimental Conditions ◽  
Non Invasive

AbstractThe tryptophan to kynurenine ratio (Trp/Kyn) has been proposed as a cancer biomarker. Non-invasive topical sampling of Trp/Kyn can therefore serve as a promising concept for skin cancer diagnostics. By performing in vitro pig skin permeability studies, we conclude that non-invasive topical sampling of Trp and Kyn is feasible. We explore the influence of different experimental conditions, which are relevant for the clinical in vivo setting, such as pH variations, sampling time, and microbial degradation of Trp and Kyn. The permeabilities of Trp and Kyn are overall similar. However, the permeated Trp/Kyn ratio is generally higher than unity due to endogenous Trp, which should be taken into account to obtain a non-biased Trp/Kyn ratio accurately reflecting systemic concentrations. Additionally, prolonged sampling time is associated with bacterial Trp and Kyn degradation and should be considered in a clinical setting. Finally, the experimental results are supported by the four permeation pathways model, predicting that the hydrophilic Trp and Kyn molecules mainly permeate through lipid defects (i.e., the porous pathway). However, the hydrophobic indole ring of Trp is suggested to result in a small but noticeable relative increase of Trp diffusion via pathways across the SC lipid lamellae, while the shunt pathway is proposed to slightly favor permeation of Kyn relative to Trp.

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