Gastrointestinal stromal tumor in ileal neobladder

Abstract  Gastrointestinal stromal tumor (GIST) is a recently described mesenchymal tumor that can develop in any portion of the gastrointestinal tract. The occurrence of a GIST in the urinary tract is rare, but GIST can present as tumor of the urinary tract or invade the urinary tract. This is the first reported case of GIST in the ileal neobladder, which presented as a submucosal tumor. The patient underwent an open exploration and partial resection of the neobladder pouch.     

Synthesis and biological activity of Substance P C-terminal hexapeptide and heptapeptide analogues

The analogues [Glu(OBzl)¹¹]SP_6–11 and [Glu(OBzl)¹¹]SP_5–11 of the C-terminal hexapeptide and heptapeptide of Substance P have been synthesized by conventional solution methods. In each analogue the SCH₃ group of Met¹¹ is replaced by the COOCH₂C₆H₅ group. The in vitro activity of both analogues has been determined on three biological preparations: guinea pig ileum (GPI), rat vas deferens (RVD), and rat portal vein (RPV). The selectivity for the different receptors has been studied by utilizing atropine-treated guinea pig ileum (GPI + At). The results showed that both analogues are mainly active on GPI through the NK-1 receptor and that both analogues are equipotent to Substance P.     

Characterisation of pre- and post-synaptic α-adrenoceptors in modulation of the rat ileum longitudinal and circular muscle activities

Previous study has shown that α_2D-adrenoceptors are involved in modulation of peristalsis in the rat ileum. The aim of the present study was to determine the tissue location of α-adrenoceptors in the rat ileum by using a recently devised method. The pre-synaptic α-adrenoceptors were characterised by measuring the potencies of agonists to inhibit transmurally-evoked (1 ms pulses, 10 Hz, 8-10 s trains) contractions of the longitudinal and circular muscles and the affinities of antagonists. Post synaptic α-adrenoceptors were identified by screening agonists and antagonists in carbachol-contracted tissues. In the circular muscle the order of potencies for inhibiting transmurally-induced contraction was: clonidine ≥ oxymetazoline ≥ UK 14,304 ≥ guanfacine > talipexole > phenylephrine > azepexole. The potency ratios relative to clonidine correlated to those previously derived using the rat ileum peristaltic reflex preparation. Most of the α-adrenoceptor agonists, however, caused only small inhibitions of the longitudinal muscle contraction in response to transmural stimulation, except phenylephrine and azepexole. RX 821002, yohimbine, rauwolscine, BRL 44408, phentolamine, idazoxan, ARC 239, and prazosin inhibited the effect of clonidine on the circular muscle response with apparent pK_B values best correlated with pK_B or pK_i values derived from the rat ileum peristaltic reflex preparation and other tissues known to have the α_2D-subtype. The rank order of potencies at inhibiting carbachol-induced responses of both muscle layers was: phenylephrine ≥ oxymetazoline > clonidine ≥ talipexole > azepexole >> guanfacine. UK 14,304 was inactive up to 10 μM. The EC₅₀ value of each agonist on the longitudinal muscle was not significantly different to the corresponding value on the circular muscle. Prazosin was more potent than yohimbine at inhibiting the relaxant effect of phenylephrine in both muscle layers of carbachol-contracted tissues. It is concluded that the recently identified α_2D-adrenoceptors of the rat ileum are located on cholinergic neurons controlling circular muscle contraction. The study also demonstrated the presence of postsynaptic α₁-adrenoceptors involved in mediating relaxation in both muscle layers. Received: 4 November 1996 / Accepted: 10 April 1997     

A Correlation Between the Permeability Characteristics of a Series of Peptides Using an in Vitro Cell Culture Model (Caco-2) and Those Using an in Situ Perfused Rat Ileum Model of the Intestinal Mucosa

In an attempt to establish an in vitro/in situ correlation of intestinal permeability data, the permeability coefficients (P _app) for a series of model peptides, which were determined using an in situ perfused rat ileum model, were compared to the permeability coefficients (P _mono) determined using an in vitro cell culture model (Caco-2). The model peptides, which were all blocked on the N-terminal (acetyl, Ac) and the C-terminal (amide, NH2) ends, consisted of D-phenylalanine (F) residues (e.g., AcFNH₂, AcFFNH₂, AcFFFNH₂). To alter the degree of hydrogen bonding potential, the nitrogens of the amide bonds were sequentially methylated [e.g., AcFF(Me)FNH₂, AcF(Me)F(Me)FNH₂, Ac(Me)F(Me)F(Me)FNH₂, Ac-(Me)F(Me)F(Me)FNH(Me)]. These peptides were shown not to be metabolized in the in situ perfused rat ileum system. The results of the transport experiments showed that there were poor correlations between the apparent permeability coefficients (P _app) determined in an in situ perfused rat ileum model and the octanol–water partition coefficients (r = 0.60) or the hydrogen bonding numbers (r = 0.63) of these peptides. However, good correlations were observed between the in situ P _app values for these peptides and their partition coefficients in heptane–ethylene glycol (r = 0.96) and the differences in their partition coefficients between octanol–water and isooctane–water (r = 0.86). These results suggest that lipophilicity may not be the major factor in determining the intestinal permeability of these peptides and that hydrogen bonding potential may be a major contributing factor. A good correlation (r = 0.94) was also observed between the P _app values determined for these peptides in the in situ perfused ileum model and those P _mono values determined in the in vitro cell culture model (Caco-2) (Conradi et al., Pharm. Res. 8:1453–1460, 1991). These results suggest that the permeability values determined in the Caco-2 cell culture model may be a good predictor of the intestinal permeability of peptides.     

Dependence and cross-dependence in the guinea-pig myenteric plexus

Summary Chronic activation of opioid receptors results in the development of tolerance and dependence. Tolerance may be confined to a single receptor type and thus has been termed selective tolerance. The present investigation reveals that prolonged activation of an inhibitory acting receptor type not only results in dependence associated with this receptor but also brings about cross-dependence. Cross-dependence involves both opioid receptors as well as non-opioid receptors, e. g. adrenoceptors. The experimental design employed did not permit conclusions to be drawn about whether those receptors exhibiting cross-dependence also developed tolerance. Regardless of the receptors and their specific subsequent transduction systems, all the receptors which showed dependence and cross-dependence proved sensitive to pertussis toxin, suggesting a critical function of GTP-binding proteins for the development of not only opioid dependence but also for drug dependence in general. Since multiple transmitter receptors may converge on the same ion channel, the concept of convergent dependences may be linked to GTP-binding proteins. However, no conclusions can be drawn with regard to the precise biochemical mechanisms underlying dependence. Send offprint requests to R. Schulz at the above address     

Histochemical localization of NADPH-diaphorase in neurons of the pheasant ileum

Localization patterns of NADPH-diaphorase-positive neurons in the pheasant ileum were investigated using an enzyme histochemical method. NADPH-diaphorase activity in the pheasant ileum was demonstrated in neuronal cells bodies and nerve fibres. The NADPH-diaphorase-positive nerve cells showed a polygonal shape and were present solitary or arranged in groups in the submucosal and muscular layers. Nerve fibres penetrated the wall of the ileum at its serosal surface, frequently in the vicinity of ileal arterial branches. They were abundantly present in muscular and submucosal layers of the ileum forming thicker nerves. Some nerve fibres traversed the submucosa into the lamina propria mucosae to form dense nerve plexuses. Fine nerve fibres were found to penetrate into intestinal villi encompassing the crypts underneath the epithelium. We conclude that the pheasant ileum is characterized by abundance of NADPH-diaphorase-positive nerve structures which may play a significant functional role in the small intestine of the pheasant.     

Comparison of β-adrenoceptors mediating vasodilatation in canine subcutaneous adipose tissue and skeletal muscle

Blood flow changes in response to various drugs in simultaneously autoperfused canine subcutaneous adipose tissue and gracilis muscle were compared to study the vascular β-adrenoceptors. Compared to isoprenaline the β₂-selective agonist salbutamol was 4–6 times more potent as a vasodilator in the muscle than in adipose tissue. Furthermore two β₁-selective agonists (Tazolol and H80/62) caused vasodilatation in adipose tissue but not in the gracilis muscle. When given by close i.a. injection after β-adrenoceptor blockade, adrenaline was a more potent vasoconstrictor than noradrenaline in both tissues. Before β-blockade, however, noradrenaline was the more potent vasoconstrictor in the gracilis muscle whereas adrenaline was more potent in adipose tissue. Intravenous infusion of adrenaline in doses causing vasodilatation in the muscle caused vasoconstriction in adipose tissue whereas intravenous infusion of noradrenaline caused vasoconstriction in both tissues. The present findings suggest that the β-adrenoceptors mediating vasodilatation in skeletal muscle are mainly of the β₂-type, whereas β₁-adrenoceptors seem to predominate in subcutaneous adipose tissue. Since adrenaline is a much more potent β₂- than β₁-agonist, these differences point to different roles of intravascular adrenaline in the two sites. In skeletal muscle circulating adrenaline is mainly a vasodilator whereas in subcutaneous adipose tissue it mainly acts as a vasoconstrictor.     

Target sites for the inhibition of prostacyclin effect in guinea-pig ileum

Summary In the guinea-pig terminal ileum a maximally effective concentration of prostacyclin (PGI₂) (1 ol/l) induced contractions that were partially resistant to tetrodotoxin (TTX) 0.1 mol/l, to low temperature (20°C) and to atropine (30 nmol/l). Half maximum contractions evoked by PGI₂ (20 nmol/l) were abolished by TTX and by low temperature, which did not modify the response to exogenous acetylcholine (ACh), as well as by atropine. Procaine (5–500 ol/l) caused a concentration-dependent inhibition of contractions induced by PGI₂ (20 nmol/l and 1 mol/l) and by equieffective concentrations of ACh (20 nmol/l and 0.4 ol/l, respectively). The order of magnitude for this inhibition was ACh 20 nmol/l = PGI₂ 20 nmol/l > PGI₂1 mol/l > ACh 0.4 mol/l. In preparations exposed to TTX or to low temperature procaine (50 mol/l) did not affect the residual response to PGI₂ (1 mol/l). Quercetin (1 and 5 ol/l) inhibited the effect of PGI₂ and, at higher concentrations, it also caused partial depression of the responses to ACh. Quercetin did not alter TTX-resistant and low temperature-resistant contractions induced by PGI₂ 1 mol/l. Carbonyl cyanide-trifluoromethoxyphenyl hydrazone (FCCP) (0.1–1 ol/l) reduced the effect of PGI₂ and of ACh to approximately the same extent and inhibited the residual response to PGI₂ 1 mol/l in preparations treated with TTX or expressed to low temperature. The present results show that PGI₂, besides acting on cholinergic neurons, also exerts a direct effect on smooth muscle cells and FCCP can be used to block this effect. In contrast procaine and quercetin selectively inhibit the ACh-mediated component of PGI₂ action. Send offprint requests to R. M. Gaion     

Inhibitory effects of opioids in a circular muscle-myenteric plexus preparation of guinea-pig ileum

Summary The actions of opioids were examined in a strip preparation of the external muscle and myenteric plexus of the guinea-pig ileum cut parallel to the circular muscle. Contractions of the circular muscle induced by electrical stimulation of myenteric neurons were depressed in a concentration-dependent manner by the mu agonists, morphine and DAGO, and by the kappa agonist, U-50,488H. The concentrations of morphine, DAGO and U-50,488H which depressed nerve-mediated contractions by 50% (IC₅₀) were 86 nM, 11 nM and 5.0 nM, respectively. The equilibrium dissociation constants (K _D) for naloxone as an antagonist of the inhibitory effects of DAGO and of U5-0,488H were 5.6 nM and 29.4 nM, respectively. In contrast to the potent inhibitory effects of mu and kappa agonists, the delta-selective agonist, d-Pen-l-Pen, produced only weak inhibition of nerve-mediated contractions. Even at a concentration of 3 M, there was less than 50% inhibition, which was not antagonised by the delta receptor antagonist, ICI 174864. The experiments indicate that both mu and kappa opioid receptors are present on the myenteric neurons supplying the circular muscle and that delta receptors are either absent or ineffectively activated. Send offprint requests to S. M. Johnson