Histamine H1 Receptor-Mediated JNK Phosphorylation Is Regulated by Gq Protein-Dependent but Arrestin-Independent Pathways

Arrestins are known to be involved not only in the desensitization and internalization of G protein-coupled receptors but also in the G protein-independent activation of mitogen-activated protein (MAP) kinases, such as extracellular signal-regulated kinase (ERK) and c-Jun N-terminal kinase (JNK), to regulate cell proliferation and inflammation. Our previous study revealed that the histamine H1 receptor-mediated activation of ERK is dually regulated by Gq proteins and arrestins. In this study, we investigated the roles of Gq proteins and arrestins in the H1 receptor-mediated activation of JNK in Chinese hamster ovary (CHO) cells expressing wild-type (WT) human H1 receptors, the Gq protein-biased mutant S487TR, and the arrestin-biased mutant S487A. In these mutants, the Ser487 residue in the C-terminus region of the WT was truncated (S487TR) or mutated to alanine (S487A). Histamine significantly stimulated JNK phosphorylation in CHO cells expressing WT and S487TR but not S487A. Histamine-induced JNK phosphorylation in CHO cells expressing WT and S487TR was suppressed by inhibitors against H1 receptors (ketotifen and diphenhydramine), Gq proteins (YM-254890), and protein kinase C (PKC) (GF109203X) as well as an intracellular Ca2+ chelator (BAPTA-AM) but not by inhibitors against G protein-coupled receptor kinases (GRK2/3) (cmpd101), β-arrestin2 (β-arrestin2 siRNA), and clathrin (hypertonic sucrose). These results suggest that the H1 receptor-mediated phosphorylation of JNK is regulated by Gq-protein/Ca2+/PKC-dependent but GRK/arrestin/clathrin-independent pathways.

Differential regulation of histamine H1 receptor-mediated ERK phosphorylation by Gq proteins and arrestins

Gq protein-coupled histamine H1 receptors play crucial roles in allergic and inflammatory reactions, in which the phosphorylation of extracellular signal-regulated kinase (ERK) appears to mediate the production of inflammatory cytokines. ERK phosphorylation is regulated by G protein- and arrestin-mediated signal transduction pathways. Here, we aimed to explore how H1 receptor-mediated processes of ERK phosphorylation might be differentially regulated by Gq proteins and arrestins. For this purpose, we evaluated the regulatory mechanism(s) of H1 receptor-mediated ERK phosphorylation in Chinese hamster ovary cells expressing Gq protein- and arrestin-biased mutants of human H1 receptors, S487TR and S487A, in which the Ser487 residue in the C-terminal was truncated and mutated to alanine, respectively. Immunoblotting analysis indicated that histamine-induced ERK phosphorylation was prompt and transient in cells expressing Gq protein-biased S487TR, whereas it was slow and sustained in cells expressing arrestin-biased S487A. Inhibitors of Gq proteins (YM-254890) and protein kinase C (PKC) (GF109203X), and an intracellular Ca2+ chelator (BAPTA-AM) suppressed histamine-induced ERK phosphorylation in cells expressing S487TR, but not those expressing S487A. Conversely, inhibitors of G protein-coupled receptor kinases (GRK2/3) (cmpd101), β-arrestin2 (β-arrestin2 siRNA), clathrin (hypertonic sucrose), Raf (LY3009120), and MEK (U0126) suppressed histamine-induced ERK phosphorylation in cells expressing S487A, but not those expressing S487TR. These results suggest that H1 receptor-mediated ERK phosphorylation might be differentially regulated by the Gq protein/Ca2+/PKC and GRK/arrestin/clathrin/Raf/MEK pathways to potentially determine the early and late phases of histamine-induced allergic and inflammatory responses, respectively.

Roles of Astrocytic Endothelin ETB Receptor in Traumatic Brain Injury

Traumatic brain injury (TBI) is an intracranial injury caused by accidents, falls, or sports. The production of endothelins (ETs) is increased in the injured brain. ET receptors are classified into distinct types, including ET_A receptor (ET_A-R) and ET_B receptor (ET_B-R). ET_B-R is highly expressed in reactive astrocytes and upregulated by TBI. Activation of astrocytic ET_B-R promotes conversion to reactive astrocytes and the production of astrocyte-derived bioactive factors, including vascular permeability regulators and cytokines, which cause blood-brain barrier (BBB) disruption, brain edema, and neuroinflammation in the acute phase of TBI. ET_B-R antagonists alleviate BBB disruption and brain edema in animal models of TBI. The activation of astrocytic ET_B receptors also enhances the production of various neurotrophic factors. These astrocyte-derived neurotrophic factors promote the repair of the damaged nervous system in the recovery phase of patients with TBI. Thus, astrocytic ET_B-R is expected to be a promising drug target for TBI in both the acute and recovery phases. This article reviews recent observations on the role of astrocytic ET_B receptors in TBI.

Pharmacological Inhibition of Transient Receptor Potential Vanilloid 4 Reduces Vasogenic Edema after Traumatic Brain Injury in Mice

Vasogenic edema results from blood-brain barrier (BBB) disruption after traumatic brain injury (TBI), and although it can be fatal, no promising therapeutic drugs have been developed as yet. Transient receptor potential vanilloid 4 (TRPV4) is a calcium-permeable channel that is sensitive to temperature and osmotic pressure. As TRPV4 is known to be responsible for various pathological conditions following brain injury, we investigated the effects of pharmacological TRPV4 antagonists on TBI-induced vasogenic edema in this study. A TBI model was established by inflicting fluid percussion injury (FPI) in the mouse cerebrum and cultured astrocytes. Vasogenic brain edema and BBB disruption were assessed based on brain water content and Evans blue (EB) extravasation into brain tissue, respectively. After FPI, brain water content and EB extravasation increased. Repeated intracerebroventricular administration of the specific TRPV4 antagonists HC-067047 and RN-1734 dose-dependently reduced brain water content and alleviated EB extravasation in FPI mice. Additionally, real-time PCR analysis indicated that administration of HC-067047 and RN-1734 reversed the FPI-induced increase in mRNA levels of endogenous causal factors for BBB disruption, including matrix metalloproteinase-9 (MMP-9), vascular endothelial growth factor-A (VEGF-A), and endothelin-1 (ET-1). In astrocytes, TRPV4 level was observed to be higher than that in brain microvascular endothelial cells. Treatment with HC-067047 and RN-1734 inhibited the increase in mRNA levels of MMP-9, VEGF-A, and ET-1 in cultured astrocytes subjected to in vitro FPI. These results suggest that pharmacological inhibition of TRPV4 is expected to be a promising therapeutic strategy for treating TBI-induced vasogenic edema.

Roles of Lys191 and Lys179 in regulating thermodynamic binding forces of ligands to determine their binding affinity for human histamine H1 receptors

Docking simulations based on the crystal structure of human histamine H₁ receptors have predicted crucial roles of Lys191^5.39 and Lys179^ECL2, which exist at the entrance of the ligand-binding pocket, in increasing the H₁-receptor selectivity for carboxylated second-generation antihistamines via electrostatic interaction. In this study, we evaluated the roles of Lys191^5.39 and Lys179^ECL2 in regulating the thermodynamic binding forces of non-carboxylated and carboxylated antihistamines that determine their binding affinity for human H₁ receptors. The binding enthalpy and entropy of the 3 sets of non-carboxylated and corresponding carboxylated antihistamines (doxepin and olopatadine, desloratadine and loratadine, and terfenadine and fexofenadine, respectively) were estimated using the van't Hoff equation with the dissociation constants obtained from the displacement curves of the non-carboxylated and carboxylated antihistamines against the binding of [³H]mepyramine to the membrane preparations of Chinese hamster ovary cells expressing human H₁ receptors at various temperatures, ranging from 4 °C to 37 °C. We found that the affinity for carboxylated antihistamines was lower than that for the corresponding non-carboxylated compounds due to lower enthalpy-dependent electrostatic binding forces and/or entropy-dependent hydrophobic binding forces. Mutations of Lys191^5.39 and/or Lys179^ECL2 to alanine mostly increased the binding affinity for antihistamines due to a variety of changes in both enthalpy- and entropy-dependent binding forces. These results suggest that Lys191^5.39 and Lys179^ECL2 may not contribute to selectively increasing the binding affinity for carboxylated antihistamines via electrostatic interaction, but that they can negatively modulate the binding affinity for non-carboxylated and carboxylated antihistamines non-selectively by affecting their electrostatic as well as hydrophobic binding forces.

Differential Regulation of Thermodynamic Binding Forces of Levocetirizine and (S)-Cetirizine by Lys191 in Human Histamine H₁ Receptors

Cetirizine is a zwitterionic second-generation antihistamine containing R- and S-enantiomers, levocetirizine, and (S)-cetirizine. Levocetirizine is known to have a higher affinity for the histamine H₁ receptors than (S)-cetirizine; ligand-receptor docking simulations have suggested the importance of the formation of a salt bridge (electrostatic interaction) between the carboxylic group of levocetirizine and the Lys191 residue at the fifth transmembrane domain of human histamine H₁ receptors. In this study, we evaluated the roles of Lys191 in the regulation of the thermodynamic binding forces of levocetirizine in comparison with (S)-cetirizine. The binding enthalpy and entropy of these compounds were estimated from the van 't Hoff equation, by using the dissociation constants obtained from their displacement curves against the binding of [³H]mepyramine to the membrane preparations of Chinese hamster ovary cells expressing wild-type human H₁ receptors and their Lys191 mutants to alanine at various temperatures. We found that the higher binding affinity of wild-type H₁ receptors for levocetirizine than (S)-cetirizine was achieved by stronger forces of entropy-dependent hydrophobic binding of levocetirizine. The mutation of Lys191 to alanine reduced the affinities for levocetirizine and (S)-cetirizine, through a reduction in the entropy-dependent hydrophobic binding forces of levocetirizine and the enthalpy-dependent electrostatic binding forces of (S)-cetirizine. These results suggested that Lys191 differentially regulates the binding enthalpy and entropy of these enantiomers, and that Lys191 negatively regulates the enthalpy-dependent electrostatic binding forces of levocetirizine, contrary to the predictions derived from the ligand-receptor docking simulations.

Ca2+ -dependent down-regulation of human histamine H1 receptors in Chinese hamster ovary cells

G_q/11 protein-coupled human histamine H₁ receptors in Chinese hamster ovary cells stimulated with histamine undergo clathrin-dependent endocytosis followed by proteasome/lysosome-mediated down-regulation. In this study, we evaluated the effects of a sustained increase in intracellular Ca²⁺ concentrations induced by a receptor-bypassed stimulation with ionomycin, a Ca²⁺ ionophore, on the endocytosis and down-regulation of H₁ receptors in Chinese hamster ovary cells. All cellular and cell-surface H₁ receptors were detected by the binding of [³ H]mepyramine to intact cells sensitive to the hydrophobic and hydrophilic H₁ receptor ligands, mepyramine and pirdonium, respectively. The pretreatment of cells with ionomycin markedly reduced the mepyramine- and pirdonium-sensitive binding sites of [³ H]mepyramine, which were completely abrogated by the deprivation of extracellular Ca²⁺ and partially by a ubiquitin-activating enzyme inhibitor (UBEI-41), but were not affected by inhibitors of calmodulin (W-7 or calmidazolium) and protein kinase C (chelerythrine or GF109203X). These ionomycin-induced changes were also not affected by inhibitors of receptor endocytosis via clathrin (hypertonic sucrose) and caveolae/lipid rafts (filipin or nystatin) or by inhibitors of lysosomes (E-64, leupeptin, chloroquine, or NH₄ Cl), proteasomes (lactacystin or MG-132), and a Ca²⁺ -dependent non-lysosomal cysteine protease (calpain) (MDL28170). Since H₁ receptors were normally detected by confocal immunofluorescence microscopy with an antibody against H₁ receptors, even after the ionomycin treatment, H₁ receptors appeared to exist in a form to which [³ H]mepyramine was unable to bind. These results suggest that H₁ receptors are apparently down-regulated by a sustained increase in intracellular Ca²⁺ concentrations with no process of endocytosis and lysosomal/proteasomal degradation of receptors.

Reassessment of the clinical significance of portal-superior mesenteric vein invasion in borderline resectable pancreatic cancer

OBJECTIVE

The principal objective of this study is to clarify the prognostic significance of borderline resectable pancreatic cancer (BRPC). The second objective is to evaluate the prognostic impact of the depth of pathological venous invasion.

METHODS

The study included 122 pancreatic cancer patients who underwent curative surgery. All computed tomography scans of the patients were retrospectively interpreted and classified according to the NCCN guidelines, version 1.2016, as resectable (-) or borderline resectable (+) in each arterial (BR-A) and venous (BR-PV) involvement.

RESULTS

The overall survival (OS) rate was significantly higher in BR-A(-) patients (n = 94) than in BR-A(+) patients (n = 28) (P = 0.001), whereas there was no difference between BR-PV(-) (n = 101) and BR-PV(+) patients (n = 21) (P = 0.257). In a multivariate analysis, the independent predictors of OS included BR-A(+) (P = 0.002), lymph node metastasis (P = 0.008), pathological venous invasion (P = 0.003), and adjuvant chemotherapy (P = 0.001). Of 39 patients who underwent venous resection, no significant difference was observed between BR-PV(-) (n = 20) and BR-PV(+) patients (n = 19) in resection rate, lymph node metastasis, the presence of extrapancreatic nerve invasion, recurrence rate, frequency of initial recurrence at a liver or local site, and OS. Pathological venous invasion was significantly deeper in BR-PV(+) patients. However, the depth of invasion was not associated with OS.

CONCLUSION

The definition of venous involvement in the current guidelines predicted the depth of pathological venous invasion but not OS in BRPC patients. Further prospective, randomized studies are needed to establish treatment strategies for BRPC patients with isolated venous involvement.

Inhibition of Ectopic Arginine Vasopressin Production by Phenytoin in the Small Cell Lung Cancer Cell Line Lu-165

Phenytoin, a voltage-gated sodium channel (Na_V channel) antagonist, reportedly inhibits arginine vasopressin (AVP) release from an isolated rat neurohypophysis. So far, it is uncertain whether phenytoin has a direct action on ectopic AVP-producing neuroendocrine tumors. We studied the effect of phenytoin on the release of copeptin, the C-terminal fragment of pro-AVP, and expression of AVP gene in the human small cell lung cancer cell line Lu-165. Cells were maintained in RPMI1640 medium with 10% fetal bovine serum and were used within the fifth passage. Copeptin was detected using a new sandwich immunoassay, and AVP mRNA levels were measured using real-time reverse transcription polymerase chain reaction. Treatment with phenytoin at a concentration of 25 µg/mL, but not at 5 or 10 µg/mL, had an inhibitory effect on copeptin levels in the medium at 48 h. At the same concentration, AVP mRNA levels in Lu-165 cells also decreased. Although a sodium challenge with added sodium at 20 mEq/L increased copeptin levels in the medium, a sodium challenge with added sodium at 10 and 20 mEq/L had no effect on AVP mRNA levels. Phenytoin at a concentration of 25 µg/mL suppressed copeptin levels in the medium under the sodium challenge with added sodium at 10 and 20 mEq/L. Phenytoin at a concentration of 25 µg/mL also decreased AVP mRNA levels in Lu-165 cells under the sodium challenge with added sodium at 10 mEq/L, but not at 20 mEq/L. Among five tested Na_V channel subunits, Na_V1.3 was highly expressed in Lu-165 cells. However, phenytoin significantly decreased Na_V1.3 mRNA levels under the sodium challenge with added sodium at 10 and 20 mEq/L. These results suggest that Lu-165 cells are sensitive to phenytoin and sodium to control of AVP release and its gene expression. Phenytoin might have a direct action on ectopic AVP-producing tumors, suggesting the importance of Na_V channels in AVP-producing neuroendocrine tumors.

Asp73-dependent and -independent regulation of the affinity of ligands for human histamine H1 receptors by Na. Biochem Pharmacol 2016;128:46-54. [PMID: 28040476 DOI: 10.1016/j.bcp.2016.12.021]

The affinity of ligands for G-protein-coupled receptors (GPCRs) is allosterically regulated by Na⁺ via a highly conserved aspartate residue (Asp^2.50) in the second transmembrane domain of GPCRs. In the present study, we examined the Na⁺-mediated regulation of the affinity of ligands for G_q/11-protein-coupled human histamine H₁ receptors in Chinese hamster ovary cells. The affinities of 3 agonists and 20 antihistamines were evaluated by their displacement curves against the binding of [³H]-mepyramine to membrane preparations in the presence or absence of 100mM NaCl. The affinities of most drugs including histamine, an agonist, and d-chlorpheniramine, a first-generation antihistamine, were reduced by NaCl, with the extent of NaCl-mediated changes varying widely between drugs. In contrast, the affinities of some second-generation antihistamines such as fexofenadine were increased by NaCl. These changes were retained in intact cells. The mutation of Asp^2.50 (Asp73) to asparagine abrogated NaCl-induced reductions in affinities for histamine and d-chlorpheniramine, but not NaCl-induced increases in the affinity for fexofenadine. Quantitative structure-activity relationship (QSAR) analyses showed that these Na⁺-mediated changes were explained and predicted by a combination of the molecular energies and implicit solvation energies of the compounds. These results suggest that Na⁺ diversely regulates the affinity of ligands for H₁ receptors from the extracellular sites of receptors via Asp73-dependent and -independent mechanisms in a manner that depends on the physicochemical properties of ligands. These results may contribute to a deeper understanding of the fundamental mechanisms by which the affinity of ligands for their receptors is allosterically regulated by Na⁺.

C-terminal of human histamine H1 receptors regulates their agonist-induced clathrin-mediated internalization and G-protein signaling

It has been suggested that the agonist-induced internalization of G-protein-coupled receptors from the cell surface into intracellular compartments regulates cellular responsiveness. We previously reported that G_q/11 -protein-coupled human histamine H₁ receptors internalized via clathrin-dependent mechanisms upon stimulation with histamine. However, the molecular determinants of H₁ receptors responsible for agonist-induced internalization remain unclear. In this study, we evaluated the roles of the intracellular C-terminal of human histamine H₁ receptors tagged with hemagglutinin (HA) at the N-terminal in histamine-induced internalization in Chinese hamster ovary cells. The histamine-induced internalization was evaluated by the receptor binding assay with [³ H]mepyramine and confocal immunofluorescence microscopy with an anti-HA antibody. We found that histamine-induced internalization was inhibited under hypertonic conditions or by pitstop, a clathrin terminal domain inhibitor, but not by filipin or nystatin, disruptors of the caveolar structure and function. The histamine-induced internalization was also inhibited by truncation of a single amino acid, Ser487, located at the end of the intracellular C-terminal of H₁ receptors, but not by its mutation to alanine. In contrast, the receptor-G-protein coupling, which was evaluated by histamine-induced accumulation of [³ H]inositol phosphates, was potentiated by truncation of Ser487, but was lost by its mutation to alanine. These results suggest that the intracellular C-terminal of human H₁ receptors, which only comprises 17 amino acids (Cys471-Ser487), plays crucial roles in both clathrin-dependent internalization of H₁ receptors and G-protein signaling, in which truncation of Ser487 and its mutation to alanine are revealed to result in biased signaling toward activation of G-proteins and clathrin-mediated internalization, respectively.

Membrane depolarization-induced RhoA/Rho-associated kinase activation and sustained contraction of rat caudal arterial smooth muscle involves genistein-sensitive tyrosine phosphorylation

Rho-associated kinase (ROK) activation plays an important role in K⁺-induced contraction of rat caudal arterial smooth muscle (Mita et al., Biochem J. 2002; 364: 431–40). The present study investigated a potential role for tyrosine kinase activity in K⁺-induced RhoA activation and contraction. The non-selective tyrosine kinase inhibitor genistein, but not the src family tyrosine kinase inhibitor PP2, inhibited K⁺-induced sustained contraction (IC₅₀ = 11.3 ± 2.4 µM). Genistein (10 µM) inhibited the K⁺-induced increase in myosin light chain (LC₂₀) phosphorylation without affecting the Ca²⁺ transient. The tyrosine phosphatase inhibitor vanadate induced contraction that was reversed by genistein (IC₅₀ = 6.5 ± 2.3 µM) and the ROK inhibitor Y-27632 (IC₅₀ = 0.27 ± 0.04 µM). Vanadate also increased LC₂₀ phosphorylation in a genistein- and Y-27632-dependent manner. K⁺ stimulation induced translocation of RhoA to the membrane, which was inhibited by genistein. Phosphorylation of MYPT1 (myosin-targeting subunit of myosin light chain phosphatase) was significantly increased at Thr855 and Thr697 by K⁺ stimulation in a genistein- and Y-27632-sensitive manner. Finally, K⁺ stimulation induced genistein-sensitive tyrosine phosphorylation of proteins of ∼55, 70 and 113 kDa. We conclude that a genistein-sensitive tyrosine kinase, activated by the membrane depolarization-induced increase in [Ca²⁺]_i, is involved in the RhoA/ROK activation and sustained contraction induced by K⁺. Ca²⁺ sensitization, myosin light chain phosphatase, RhoA, Rho-associated kinase, tyrosine kinase

The affinity of histamine for Gq protein-coupled histamine H(1)-receptors is predominantly regulated by their internalization in human astrocytoma cells

We examined the regulatory mechanisms of the affinity of Gq protein-coupled histamine H(1)-receptors for histamine after histamine pretreatment in intact human U373 MG astrocytoma cells. In control cells, the displacement curves for histamine against the binding of 5 nM [(3)H]mepyramine, a radioligand for H(1)-receptors, showed the presence of two binding sites for histamine, that is, high and low affinity sites. Pretreatment with 0.1 mM histamine for 30 min at 37°C induced a significant reduction in the percentage of high affinity sites for histamine and a concomitant increase in the percentage of low affinity sites with no change in their pIC(50) values. These histamine-induced changes were insensitive to 30 µM KN-62, an inhibitor of Ca(2+)/calmodulin-dependent protein kinase II, but they were completely inhibited either by 0.4 mM ZnCl(2), an inhibitor of G protein-coupled receptor kinases (GRKs), or under hypertonic conditions, where clathrin-mediated endocytosis is known to be inhibited. These results suggest that histamine-induced conversion of high to low affinity sites for histamine is predominantly regulated by GRK/clathrin-mediated internalization of H(1)-receptors in human astrocytoma cells.

Impairment of α1-adrenoceptor-mediated contractile activity in caudal arterial smooth muscle from type 2 diabetic Goto-Kakizaki rats

1. In the present study, we compared the responsiveness of de-endothelialized caudal artery smooth muscle strips, isolated from Type 2 diabetic Goto-Kakizaki (GK) and normal Wistar rats, to alpha(1)-adrenoceptor stimulation (cirazoline) and membrane depolarization (K(+)). 2. The contractile and myosin 20 kDa light chain (LC(20)) phosphorylation responses to 0.3 micromol/L cirazoline of caudal artery strips isolated from 12-week-old GK rats were significantly reduced compared with those of age-matched Wistar rats, whereas the contractile and LC(20) phosphorylation responses to 60 mmol/L K(+) were unaltered. 3. Stimulation of fura 2-AM-loaded strips from GK rats with 0.3 micromol/L cirazoline induced a significantly smaller rise in [Ca(2+)](i) (by approximately 20%) compared with that in strips from Wistar rats, whereas comparable Ca(2+) transients were evoked by K(+) in both. 4. Using quantitative polymerase chain reaction, no significant differences were detected in the mRNA expression of alpha(1A)-, alpha(1B)- and alpha(1D)-adrenoceptor subtypes between GK and Wistar rats. 5. Cirazoline (1 micromol/L)- and caffeine (20 mmol/L)-induced contractions in the absence of extracellular Ca(2+) were unaltered in GK rats, suggesting that the release of Ca(2+) from the sarcoplasmic reticulum in response to cirazoline does not differ between GK and Wistar rats. 6. The results of the present study suggest that Ca(2+) entry from the extracellular space via alpha(1)-adrenoceptor-activated, Ca(2+)-permeable channels, but not via membrane depolarization and voltage-gated L-type Ca(2+) channels, is impaired in caudal artery smooth muscle of GK rats.

DESENSITIZATION OF GUINEA-PIG TAENIA CAECI SMOOTH MUSCLE INDUCED BY A LOW CONCENTRATION OF CARBACHOL

1. In guinea-pig taenia caeci smooth muscle we have found that 10(-4) mol/L carbachol-induced desensitization to muscarinic agonists develops within 15-30 s, followed by transient resensitization at 1 min, whereas the desensitization to depolarizing high K(+) develops with maximal desensitization at 1 min followed by sustained resensitization up to 30 min. In both cases, Ca(2+)-dependent processes play a crucial role in determining the development of desensitization. 2. To elucidate whether these peculiar processes of desensitization/resensitization may be induced by a lower concentration of carbachol, we examined the development of desensitization induced by 10(-6) mol/L carbachol, because at this concentration carbachol is known to induce biphasic changes in intracellular Ca(2+) concentrations, with a smaller transient increase followed by a larger sustained increase than seen with 10(-4) mol/L carbachol. 3. Contractile responses to muscarinic agonists (carbachol or AHR-602) and high K(+) were desensitized by pretreatment with 10(-6) mol/L carbachol for 30 min in a manner dependent on the presence of extracellular Ca(2+). 4. The development of 10(-6) mol/L carbachol-induced desensitization to these muscarinic agonists in the presence of extracellular Ca(2+) showed three successive phases: fast desensitization within 30 s, followed by transient resensitization at 1 min and the subsequent development of desensitization up to 30 min. In contrast, desensitization to high K(+) did not develop up to 10 min and significant desensitization occurred at 30 min, with no apparent resensitization phase. 5. These results suggest that the characteristics of the Ca(2+)-dependent development of desensitization to muscarinic agonists, but not to high K(+), are well maintained in desensitization induced by a lower concentration of carbachol.

DIFFERENTIAL DEVELOPMENT OF CARBACHOL-INDUCED DESENSITIZATION IN RECEPTOR-MEDIATED Ca2+INFLUX AND Ca2+RELEASE PATHWAYS IN SMOOTH MUSCLE OF GUINEA-PIG TAENIA CAECI

1. We have found that development of carbachol (CCh)-induced desensitization to receptor agonists, but not to receptor by-passed stimulation, is transiently interrupted by a Ca2+-dependent resensitization during the early stage in the smooth muscle of guinea-pig taenia caeci. To further characterize the receptor-mediated signal transduction pathways involved in this peculiar desensitization process, we examined the desensitization processes during Ca2+ influx- and Ca2+ release-mediated contractions in response to activation of muscarinic receptors or histamine H1 receptors. 2. Desensitization treatment with 10(-4) mol/L CCh for 30 min in the presence of extracellular Ca2+ resulted in desensitization to the muscarinic agonists McN-A-343 or AHR-602, which are known to induce contraction only in the presence of extracellular Ca2+ in taenia caeci. The development of desensitization to these agonists was interrupted by a transient resensitization at 1 min. In contrast, the transient resensitization phase was lost following removal of extracellular Ca2+ during the desensitization treatment with CCh; under these conditions, the desensitization developed gradually without an apparent resensitization phase. 3. Contractions to 10(-4) mol/L CCh and 10(-4) mol/L histamine in the absence of extracellular Ca2+ were gradually desensitized without a resensitization phase following the CCh desensitization treatment, irrespective of the presence or absence of extracellular Ca2+ during CCh treatment, although the onset of the desensitization was delayed under Ca2+-free conditions. 4. These results suggest that the receptor-mediated Ca2+ influx and Ca2+ release pathways are differentially desensitized to CCh and that the transient resensitization appears to regulate the desensitization process in response to Ca2+ influx-mediated contraction. Such differential processes of desensitization in receptor-mediated bifurcated signalling pathways may determine cellular responsiveness to certain types of stimuli, depending on the different Ca2+ sources required for contraction.

Ca2+-dependent differential development of carbachol-induced desensitization to receptor agonists and high K+ in guinea-pig taenia caeci

1. Carbachol (CCh)-induced desensitization to CCh was interrupted by a transient resensitization during its early stage, with concomitant changes at the muscarinic receptor/G-protein level in smooth muscle of guinea-pig taenia caeci. To assess whether such a peculiar desensitizing process may heterologously regulate smooth muscle contraction, we examined the developmental processes of CCh-induced desensitization to histamine and high K(+) and compared it with that to CCh. 2. Under Ca(2+)-containing physiological conditions, treatment with 10(-4) mol/L CCh for 30 min induced heterologous desensitization to histamine and high K(+). The development of desensitization to histamine was interrupted by a transient resensitization at 1 min in a manner similar to that to CCh. In contrast, CCh-induced desensitization to high K(+) reached a peak at 1 min and was followed by a gradual resensitization up to a partial restoration at 30 min. 3. Under Ca(2+)-free conditions containing 0.2 mmol/L EGTA, treatment with 10(-4) mol/L CCh for 30 min failed to induce heterologous desensitization to either histamine or high K(+), whereas the CCh treatment developed homologous desensitization to CCh in a simple time-dependent manner without a resensitization phase. 4. These results suggest that cellular responsiveness to receptor agonists and non-receptor-mediated depolarizing stimulation is differentially regulated by Ca(2+)-dependent heterologous desensitization in smooth muscle.

Differential roles of ryanodine- and thapsigargin-sensitive intracellular CA2+ stores in excitation-contraction coupling in smooth muscle of guinea-pig taenia caeci

1. To explore roles of intracellular Ca(2+) stores in excitation-contraction coupling in smooth muscle, we examined the effects of ryanodine, a fixer of ryanodine receptor-Ca(2+) channels to an open state, and thapsigargin, a selective inhibitor of the Ca(2+) pump in the intracellular stores, on smooth muscle contraction in the presence and absence of extracellular Ca(2+) in guinea-pig taenia caeci. 2. In Ca(2+) -free solution, contractions induced by 0.1 mmol/L carbachol and 0.1 mmol/L histamine were reduced to approximately 65% of control by either 1 micro mol/L thapsigargin or 10 micro mol/L ryanodine. In contrast, caffeine-induced contraction was reduced to approximately 40% of control by ryanodine, but was not affected by thapsigargin. 3. In the presence of extracellular Ca(2+), thapsigargin slowly induced a large and sustained contraction. In contrast, ryanodine did not induce an apparent contraction, but increased the sensitivity of contractile responses to receptor agonists (carbachol, AHR-602 and histamine) or depolarizing high K(+) with no changes in the maximal contraction. 4. These results suggest that there are pharmacological and physiological differences between ryanodine- and thapsigargin-sensitive intracellular Ca(2+) stores in excitation-contraction coupling in smooth muscle, which may be responsible for their differential effects on the Ca(2+) -influx pathway.

Cloning and characterization of novel snake venom proteins that block smooth muscle contraction

In this study, we isolated a 25-kDa novel snake venom protein, designated ablomin, from the venom of the Japanese Mamushi snake (Agkistrodon blomhoffi). The amino-acid sequence of this protein was determined by peptide sequencing and cDNA cloning. The deduced sequence showed high similarity to helothermine from the Mexican beaded lizard (Heloderma horridum horridum), which blocks voltage-gated calcium and potassium channels, and ryanodine receptors. Ablomin blocked contraction of rat tail arterial smooth muscle elicited by high K+-induced depolarization in the 0.1-1 microm range, but did not block caffeine-stimulated contraction. Furthermore, we isolated three other proteins from snake venoms that are homologous to ablomin and cloned the corresponding cDNAs. Two of these homologous proteins, triflin and latisemin, also inhibited high K+-induced contraction of the artery. These results indicate that several snake venoms contain novel proteins with neurotoxin-like activity.

Membrane depolarization-induced contraction of rat caudal arterial smooth muscle involves Rho-associated kinase

Depolarization of the sarcolemma of smooth muscle cells activates voltage-gated Ca2+ channels, influx of Ca2+ and activation of cross-bridge cycling by phosphorylation of myosin catalysed by Ca2+/calmodulin-dependent myosin light-chain kinase (MLCK). Agonist stimulation of smooth muscle contraction often involves other kinases in addition to MLCK. In the present study, we address the hypothesis that membrane depolarization-induced contraction of rat caudal arterial smooth muscle may involve activation of Rho-associated kinase (ROK). Addition of 60 mM K+ to de-endothelialized muscle strips in the presence of prazosin and propranolol induced a contraction that peaked rapidly and then declined to a steady level of force corresponding to approx. 30% of the peak contraction. This contractile response was abolished by the Ca2+-channel blocker nicardipine or the removal of extracellular Ca2+. An MLCK inhibitor (ML-9) inhibited both the phasic and tonic components of K+-induced contraction. On the other hand, the ROK inhibitors Y-27632 and HA-1077 abolished the tonic component of K+-induced contraction, and slightly reduced the phasic component. Phosphorylation levels of the 20-kDa light chain of myosin increased rapidly in response to 60 mM K+ and subsequently declined to a steady-state level significantly greater than the resting level. Y-27632 abolished the sustained and reduced the phasic elevation of the phosphorylation of the 20-kDa light chain of myosin, without affecting the K+-induced elevation of cytosolic free Ca2+ concentration. These results indicate that ROK activation plays an important role in the sustained phase of K+-induced contraction of rat caudal arterial smooth muscle, but has little involvement in the phasic component of K+-induced contraction. Furthermore, these results are consistent with inhibition of myosin light-chain phosphatase by ROK, which would account for the sustained elevation of myosin phosphorylation and tension in response to membrane depolarization.

Ca(2+)/calmodulin-mediated regulation of the desensitizing process in G(q) protein-coupled histamine H(1) receptor-mediated Ca(2+) responses in human U373 MG astrocytoma cells

We investigated Ca(2+)/calmodulin (CaM)-mediated regulation of the desensitizing process of the histamine H(1) receptor-mediated increase in intracellular Ca(2+) concentration in human U373 MG astrocytoma cells. The desensitizing process was evaluated by measuring the histamine-induced Ca(2+) responses in cells pretreated with histamine for 15 s-30 min under various conditions. Under normal physiological conditions, desensitization developed with three successive phases : a fast desensitization within 15 s, a transient resensitization at 45 s, and a prompt and sustained redesensitization from 1 to 30 min. Similar processes of desensitization/resensitization occurred even under hypertonic conditions, where histamine-mediated internalization of the histamine H(1) receptor is inhibited. The transient resensitization phase was selectively prevented by deprivation of extracellular Ca(2+) and, even more strikingly, by the presence of W-7 (a CaM antagonist). FK506 and cyclosporin A, Ca(2+)/CaM-dependent protein phosphatase (PP2B) inhibitors, mimicked such effects. In the presence of KN-62, a Ca(2+)/CaM-dependent protein kinase II (CaM kinase II) inhibitor, the early development of desensitization disappeared, allowing a slow and simple development of desensitization. The early processes of desensitization and resensitization were unaffected by W-5, okadaic acid, and KN-04 (less potent inhibitors against CaM, PP2B, and CaM kinase II, respectively) or by GF109203X and chelerythrine (protein kinase C inhibitors). The high-affinity site for histamine was converted to a lower-affinity site by histamine treatment, which also showed a transient restoration phase at 45 s in a manner sensitive to KN-62 and FK506. These results provide the first evidence that Ca(2+)/CaM plays a crucial role in determining the early phase of the desensitizing process via activation of CaM kinase II and PP2B, by regulating agonist affinity for histamine H(1) receptors.

Isolation and characterization of the murine cardiotrophin-1 gene: expression and norepinephrine-induced transcriptional activation

Cardiotrophin-1 (CT-1) is a novel cytokine capable of inducing hypertrophy in cardiac myocytes and belongs to the interleukin-6 family that exert their biological effects through gp130. To clarify the involvement and pathophysiological role of CT-1 in myocardial diseases, it is important to characterize the regulation of CT-1 gene expression. In this study, we isolated and characterized the mouse CT-1 gene and studied the expression of CT-1 mRNA under norepinephrine (NE) stimulation. The mouse CT-1 gene constitutes 5.4 kilobases (kb) in length and consists of three exons and two introns. When nucleotide sequences of the coding regions of exons were compared with those of human, exon 1, 2 and 3 share 96%, 84% and 81% homology, respectively. The 2.2 kb of 5; flanking lesion of the mouse CT-1 gene contains a variety of transcription factor binding motif (e.g. CREB, MyoD, NF-IL6, Nkx2.5, GATA). Fluorescent in situ hybridization (FISH) analysis demonstrated that the mouse CT-1 gene was located on chromosome 7F3. The expression of CT-1 mRNA in cardiac myocytes was markedly augmented by NE stimulation, both in vivo and in vitro. Promoter analysis using deletion constructs of the CT-1 gene indicated that the NE responsive element located between -2174/-1540 and this region contained the cAMP responsive element (CRE). Electrophoretic gel mobility shift assays showed enhanced binding activity to the CRE motif in the nuclear extracts from NE-stimulated cardiac myocytes. These studies indicate that CT-1 is abundantly expressed in the heart and that the CRE is a possible cis -acting element of the CT-1 gene under NE-stimulation. These data suggest that the CT-1 gene expression is regulated, at least partially, by transcriptional machinery.

5-fluorouracil sensitivity and dihydropyrimidine dehydrogenase activity in advanced gastric cancer

BACKGROUND

Dihydropyrimidine dehydrogenase (DPD) is the rate-limiting enzyme of 5-fluorouracil (5-FU) catabolism. Several studies have demonstrated the clinical importance of DPD in cancer patients, suggesting that the efficacy of 5-FU may be related to DPD activity in tumor tissue. In the present study, DPD activity and chemosensitivity to 5-FU were evaluated in advanced gastric cancer.

MATERIALS AND METHODS

Thirty-four gastric cancers from 32 patients were studied and chemosensitivity to 5-FU was evaluated by histoculture drug response assay.

RESULTS AND CONCLUSION

DPD activity and tumor inhibition of 5-FU among all cases showed no significant correlation, but among 14 histologically differentiated cases significant correlation was observed. DPD activity may be useful in determining the 5-FU sensitivity of differentiated gastric cancer.

Expressional patterns of cytokines in a murine model of acute myocarditis: early expression of cardiotrophin-1

To determine the role of cytokines in acute myocarditis, we examined expressional patterns of cardiotrophin-1 (CT-1), TNF-alpha, and IL-1alpha in a murine model of acute myocarditis. Ten-day-old Institute of Cancer Research mice were injected with Coxsackievirus B3 and killed on Days 1, 2, 3, 4, 5, 7, 10, 14, and 28 of injection. TNF-alpha and IL-1alpha expressions were investigated on histological sections from each heart, and mRNA expression of TNF-alpha, IL-1alpha, and CT-1 in the heart was examined by reverse transcription-polymerase chain reaction and RNase protection assay. To determine myocardial regeneration, cardiomyocytic DNA synthesis was investigated using bromodeoxyuridine on Days 3, 5, 7, and 10, and the labeling index was calculated in each heart. Age-matched uninfected mice were used as controls. TNFalpha and IL-1alpha expression was first detected in the cardiomyocytes on Day 3 and reached the maximum level on Day 7, when inflammatory changes were most prominent. Although an increased expression of TNFalpha and IL-1alpha mRNA was also detected on Day 3, CT-1 mRNA expression was distinctly augmented on Day 2. The labeling indices in the hearts with myocarditis were significantly higher than in those of the controls in all of the time points examined. CT-1 expression preceded TNF-alpha and IL-1alpha expressions and active DNA synthesis in a murine model of acute myocarditis. All CVB3-infected mice with anti-glycoprotein-130 antibody treatment died within 6 days. CT-1 may exert a protective role by modulating cytokine production and by inducing cardiomyocytic proliferation in CVB3-infected murine hearts.

[Difficulty in using RP, PL, and EW factors in the Japanese classification of pancreatic carcinoma]

The classification of pancreatic carcinoma by the Japan Pancreas Society reflects the prognosis of each stage better than does the TMN classification. On the other hand, there are too many factors to examine in the Japanese system, some of which are difficult to use and have low accuracy in pre- and/or intraoperative diagnosis (RP and PL), and their analysis requires various specimen handling procedures (EW). We propose that: 1) a simple, easy decision flow chart be established for ew and 2) EW/ew be designated as (-) or (+) and for EW/ew (+) cases other factors (ly, v, pl, and direct tumor invasion) be added (for example, ew (+)-pl).

Hypoxic stress induces cardiotrophin-1 expression in cardiac myocytes

Cardiotrophin-1 (CT-1), a novel cytokine that belongs to the interleukin-6 cytokine family, activates gp130 dependent signaling pathway to transduce hypertrophic and cytoprotective signals in cardiac myocytes. To investigate the pathophysiological significance of CT-1 in myocardial disease, the expression of CT-1 was examined after hypoxic stimulation in cardiac myocytes. Highly expressed CT-1 mRNA was observed in embryonic and adult hearts by RNase protection assay. Cardiac myocytes subjected to hypoxic stimulation augmented CT-1 mRNA expression. Although CT-1 mRNA was expressed to a higher extent in non-myocardial cells, the expression was not affected with the stimulation. Conditioned medium from cultured cardiac myocytes presented the ability to tyrosine phosphorylate STAT3 through gp130 and that was further augmented with hypoxic conditioned medium. These results demonstrated for the first time that CT-1 expression is augmented after hypoxic stimulation and hypoxic conditioned medium presented enhanced ability to activate STAT3 in cardiac myocytes. CT-1 might play an important role in the pathogenesis of ischemic heart disease.

Evaluation of pylorus-preserving pancreatoduodenectomy with the Imanaga reconstruction by hepatobiliary and gastrointestinal dual scintigraphy

BACKGROUND

Following pylorus-preserving pancreatoduodenectomy (PPPD), most surgeons use gastrointestinal reconstruction with an end-to-side duodenojejunostomy placed distally to the pancreatojejunostomy and choledochojejunostomy. In contrast, the authors have consistently used PPPD with the Imanaga reconstruction (PPPD-Imanaga) which consists of end-to-end duodeno- jejunostomy, end-to-side pancreatojejunostomy and choledochojejunostomy, performed in that order. In this study, the movement of bile and food after PPPD-Imanaga was evaluated to document the functional advantages of this method.

METHODS

Twenty-four patients who had undergone PPPD-Imanaga were subjected to hepatobiliary and gastrointestinal dual scintigraphy. The interval between operation and scintigraphy ranged from 28 days to 67 months. Six of the 24 patients underwent repeated dual scintigraphy for the observation of temporal changes in gastrointestinal function.

RESULTS

The incidence of biliogastric reflux and bile stasis in the jejunal loop was markedly decreased at times later than 2 months after operation. Delay of gastric emptying and bile evacuation, sometimes accompanied by stasis in the jejunal loop, affected the mixing status of bile and food at 1 h after the beginning of imaging. A majority of the patients, however, had a satisfactory mixing status at 2 h.

CONCLUSION

The Imanaga reconstruction appears to be a recommendable procedure following PPPD, in light of the bile and food movement achieved in the gastrointestinal tract.

Ca2+/calmodulin-mediated regulation of agonist-induced sequestration of Gq protein-coupled histamine H1 receptors in human U373 MG astrocytoma cells

We investigated the regulation by intracellular Ca2+ of agonist-induced sequestration of Gq protein-coupled histamine H1 receptors in human U373 MG astrocytoma cells. Histamine-induced sequestration of H1 receptors from the cell surface membrane was detected as the loss of [3H]mepyramine binding sites on intact cells accessible to the hydrophilic H1-receptor antagonist pirdonium. The changes in the pirdonium-sensitive binding of [3H]mepyramine were mirrored by changes in the subcellular distribution of H1 receptors detected by sucrose density gradient centrifugation. The histamine-induced sequestration of H1 receptors did not occur in hypertonic medium, in which clathrin-mediated endocytosis is known to be inhibited, but was significantly accelerated in the absence of extracellular Ca2+ or in the presence of the calmodulin antagonists W-7 and calmidazolium. Inhibitors of protein kinase C (H-7 and GF109203X), Ca2+/calmodulin-dependent protein kinase II (KN-62), or protein phosphatase 2B (FK506) did not alter the time course of H1-receptor sequestration. These results provide the first evidence that agonist-induced, clathrin-mediated sequestration of Gq protein-coupled receptors is transiently inhibited by Ca2+/calmodulin, with the result that receptors remain on the cell surface membrane during the early stage of agonist stimulation.

Results of surgery and adjuvant radiotherapy for pancreatic cancer

We retrospectively reviewed the cases of 34 patients with pancreatic cancer who underwent resection between January 1988 and December 1996. Adjuvant radiotherapy was performed in 24 patients, with 13 receiving both intra- and postoperative radiotherapy, 2 receiving postoperative radiotherapy (PORT) alone, and 9 receiving intraoperative radiotherapy (IORT) alone. The 1- and 3-year survival rates for all 34 patients were 59% and 19%, respectively, with a median survival of 13 months. At the time of the analysis, three patients were still alive. Recurrence patterns were assessed in 25 patients who had had no distant metastases at the time of surgery, had survived more than 3 months after surgery, and had undergone close surveillance for recurrence. Based on computed tomography (CT) and autopsy findings, a total of 15 (60%) of these 25 patients had local recurrence, 13 (52%) had liver metastases, and 8 (32%) had both. Eight (62%) of the 13 patients who received IORT and/or PORT developed local recurrence, and we failed to detect any survival advantage of IORT and/or PORT over surgery alone. However, autopsies revealed a suppressive effect of radiation on cancer growth, and local recurrence was not considered to be the direct cause of death in any of the patients, nor did any of the patients develop gastrointestinal obstruction due to local recurrence. The incidence of liver metastasis in the patients with and without tumor invasion of the portal system was 80% (8/10) and 33% (5/15), respectively. The patients who did not develop liver metastasis had significantly longer survivals than who did. Further improvements of survival await effective prophylactic treatment for liver metastases.

Preoperative radiotherapy for cancer of the extrahepatic bile duct

From January 1988 through June 1996, 12 patients who had extrahepatic bile-duct cancer received preoperative radiotherapy at doses of 40.6 Gy to 58.4 Gy. At restaging, 1 patient was found to have liver metastases and the remaining 11 patients were taken to surgery. Nine patients underwent resection, and 8 of the 9 received intraoperative radiotherapy. Complications occurred in 4 patients, 3 of whom died postoperatively. The 2 patients who died of intraabdominal complications received both preoperative radiation doses of more than 55 Gy and intraoperative radiotherapy doses of 14 Gy or more. Histologic evidence of irradiation effects was present in all specimens. Irradiation effects on perineural invasion were observed in varying degrees. Two of the four patients who had marked irradiation effects on perineural invasion developed local recurrence, which was found at autopsy to have infiltrated the hepatic hilum without obstructing the hepatic ducts. One patient who had minimal irradiation effects on perineural invasion developed local recurrence with obstructing the hepatic ducts. Of the 2 patients who had positive margins, the patient with marked irradiation effects on perineural invasion survived 18 months, but the patient with slight irradiation effects on perineural invasion survived only 5 months. The high complication rate requires modification of this strategy. The propriety of combining preoperative radiotherapy with intraoperative radiotherapy as well as the radiation dose should be reinvestigated.

Complications after pylorus-preserving pancreatoduodenectomy with gastrointestinal reconstruction by the Imanaga method

BACKGROUND

Pylorus-preserving pancreatoduodenectomies (PPPDs) have been performed for disorders of the pancreatic head and periampullary region. The most commonly used reconstructive technique anastomoses the duodenum end-to-side to the jejunum, with pancreatic and biliary anastomoses placed proximally to the end-to-side duodenojejunostomy. In contrast, we have favored PPPD with gastrointestinal reconstruction by the Imanaga method (PPPD-Imanaga), which consists of end-to-end duodenojejunostomy, end-to-side pancreatojejunostomy, and choledochojejunostomy, performed in that order, because the PPPD-Imanaga provides a physiologic mixture of food, pancreatic juice, and bile in the upper portion of the jejunum.

STUDY DESIGN

To identify their postoperative complications, we retrospectively reviewed the cases of 55 patients who underwent a PPPD-Imanaga between December 1986 and December 1996. In all cases, the right gastric artery was divided and the pancreatic duct was sewn directly to a small opening in the jejunal mucosa. Twenty patients with malignancy received adjuvant radiotherapy.

RESULTS

Five patients died without being discharged, including one who died of cancer progression, for a postoperative mortality rate of 9%. These deaths were limited to patients who had received adjuvant radiotherapy, with only two deaths being procedure related. Delayed gastric emptying, pancreatic leak, and marginal ulcer were observed in 25 (45%), 3 (5%), and 3 (5%) patients, respectively. The delay in gastric emptying was transient and resolved spontaneously, with no patients undergoing reoperation. Only one patient required a reoperation, for the control of intraabdominal bleeding.

CONCLUSIONS

A PPPD-Imanaga can be performed with acceptable morbidity and mortality risks. We conclude that the Imanaga method is a favorable complement to PPPD.

Contrasting effects of carbachol, McN-A-343 and AHR-602 on Ca(2+)-mobilization and Ca(2+)-influx pathways in taenia caeci

1. We compared the binding profiles and contractile mechanisms of putative muscarinic M1 agonists McN-A-343 and AHR-602 with those of carbachol in smooth muscle of guinea-pig taenia caeci. 2. McN-A-343 and AHR-602, as well as carbachol, completely displaced the atropine-sensitive binding of [3H]-quinuclidinyl benzilate to muscarinic receptors present in the membrane preparation. The potency order for the affinity of these agents for muscarinic receptors was carbachol > McN-A-343 >> AHR-602. 3. In the presence of 2.2 mM extracellular Ca2+, McN-A-343 and AHR-602 induced contraction corresponding to 79 and 85%, respectively, of the maximal contraction to 0.1 mM carbachol. Contractions induced by these agents were mediated via activation of the muscarinic receptor subtype that had a high affinity for 4-DAMP (M3 selective) but a low affinity for pirenzepine (M1 selective) and AF-DX 116 (M2 selective). These contractions were inhibited by an L-type Ca2+ channel blocker, verapamil. 4. In Ca(2+)-free solution containing 2 mM EGTA, carbachol elicited a transient contraction whereas no contraction was observed in response to McN-A-343 and AHR-602. Application of McN-A-343 or AHR-602 inhibited the carbachol-induced contraction in Ca(2+)-free solution, and this inhibition was surmounted by a higher concentration of carbachol. 5. The EC50 value for carbachol-induced contraction in the presence of extracellular Ca2+ was approximately 175 times lower than that in the absence of Ca2+. After treatment with propylbenzilylcholine mustard, carbachol induced contraction only in the presence of extracellular Ca2+. 6. The results suggest that in the taenia caeci there is a greater receptor reserve for muscarinic M3 receptor-mediated Ca2+ influx than for M3 mediated Ca2+ release. The compounds McN-A-343 and AHR-602 are agonists of the Ca2+ influx pathway, but do not appear to stimulate the Ca2+ release pathway.

[Indication and results of pancreatectomy with combined resection of vessels for adenocarcinoma of the pancreas]

Of 192 patients who received pancreatectomy for invasive adenocarcinoma of the pancreas, 107 (55. 7%) underwent combined resection of vessels at Keio University Hospital and Tochigi Cancer Center, from July 1974 until March 1996. Vascular resections included the portal and/or mesenteric vein in 103, the common hepatic artery in 14, the superior artery in 2 and the celiac axis in 5 cases. The morbidity and mortality rate are 20.2%, 1.2% in the standard resected group and 23.1%, 5.6% in the vessel resected group, respectively. Comparison of the survival rate of curability A and B patients between two groups shows no significant difference. Six patients who underwent resection of the portal and/or mesenteric vein survived more than 5 years. The longest survivor is living 13 years 6 months after surgery. Among the patients who underwent resection of the artery, two patients survived 44 and 22 months after distal pancreatectomy with resection of the celiac axis and the common hepatic artery preserving whole stomach.

Morgagni hernia diagnosed by MRI

We herein present a patient with Morgagni hernia which was diagnosed by magnetic resonance imaging (MRI). The patient had a progressively enlarging mass in the right cardiophrenic angle on chest roentgenogram. On computed tomography (CT) scans, the mass was revealed to have fat density and therefore was suspected to be either a lipoma or liposarcoma. MRI clearly demonstrated that the mass shadow was composed of omental fat herniating into the right thorax through the diaphragmatic hiatus. MRI is thus considered to be a useful noninvasive modality for the evaluation of lower anterior mediastinal masses demonstrating fat density on CT.

[Two cases of von Recklinghausen's disease with diffuse pulmonary changes]

Two patients with von Recklinghausen's disease had diffuse pulmonary diseases. The pulmonary diseases were interstitial fibrosis and emphysematous bullae. In case 2, examination of a specimen obtained by transbronchial lung biopsy revealed fibrotic interstitial thickening and adenomatous hyperplasia. Diffuse pulmonary abnormalities in von Recklinghausen's disease have been said to be fibrotic changes and emphysematous changes, as shown in roentgenograms in these two cases. The biopsy specimen obtained in case 2, however, revealed fibrotic changes only, which could not be distinguished from findings in cases of idiopathic interstitial pneumonia. In case 2, bronchoalveolar lavage fluid was also examined but it did not reveal any unique features of von Recklinghausen's disease. Since 1978, von Recklinghausen's disease has been diagnosed 10 times in our hospital, but diffuse pulmonary diseases was seen in only two of those 10 cases.

Characteristics of the binding of [3H]-mepyramine to intact human U373 MG astrocytoma cells: evidence for histamine-induced H1-receptor internalisation

1. The kinetics of the binding of 5 nM [3H]-mepyramine to sites on intact human U373 MG astrocytoma cells, sensitive to inhibition by 2 microM pirdonium, were temperature-dependent. At 37 degrees C the half-time for association was 0.9 +/- 0.4 min and at 4 degrees C 19 +/- 3 min. Dissociation of bound [3H]-mepyramine was fast at 37 degrees C, t0.5 1.5 +/- 0.3 min, but at 6 degrees C dissociation initiated by dilution or addition of unlabelled mepyramine was negligible over 120 min. The very slow dissociation at 6 degrees C made it possible to reduce the level of pirdonium-insensitive binding from 56 +/- 5% to 39 +/- 5% by washing the cells in ice-cold medium before filtration. 2. The binding of [3H]-mepyramine sensitive to 2 microM temelastine, measured after 10 min equilibration at 37 degrees C, failed to saturate and was resolved into an hyperbola and an apparently linear component, whereas the fit to the binding of [3H]-mepyramine sensitive to 2 microM pirdonium was not significantly improved over that to an hyperbola. The mean Kd for the binding of [3H]-mepyramine to the saturable component, 2.5 +/- 0.4 nM, was in close agreement with the value of 3.5 nM for mepyramine derived from inhibition of histamine H1-receptor-mediated inositol phosphate formation in U373 MG cells. 3. Curves for the inhibition of the binding of 5 nM [3H]-mepyramine to U373 MG cells by histamine H1-receptor antagonists were biphasic and were fitted to a two site-model. Affinities calculated from the best-fit IC50 values for the high-affinity site correlated well with those expected for binding to H1-receptors. 4. The percentages of the high-affinity site in curves of the inhibition of [3H]-mepyramine binding to intact U373 MG cells by two tertiary amine antagonists, norpirdonium and 4-methyldiphenhydramine, 68 +/- 3 and 63 +/- 4%, were significantly greater than the percentages of the high-affinity site in the inhibition curves of their quaternary derivatives, 50 +/- 1 and 45 +/- 3%, respectively. Similarly, the percentage of the high-affinity site for unlabelled mepyramine, 65 +/- 7%, was greater than for the non-cell penetrant H1-antagonist temelastine, 42 +/- 5%. 5. Incubation of U373 MG cells with 100 microM histamine at 37 degrees C, followed by washing twice in ice-cold medium and then incubation with 1-15 nM [3H]-mepyramine for 120 min at 4 degrees C, resulted in a decrease in the binding of [3H]-mepyramine sensitive to 2 microM pirdonium, compared to control cells not exposed to histamine. The binding of [3H]-mepyramine in the absence of pirdonium was not altered by histamine pretreatment, whereas the level of the pirdonium-insensitive binding was significantly increased, except after 1 min exposure to histamine. The decreases in the pirdonium-sensitive binding after 5, 10 and 60 min incubation with 100 microM histamine were 41 +/- 6, 56 +/- 6 and 67 +/- 8%, respectively, but the decrease after 1 min incubation with histamine, 16 +/- 8%, was not statistically significant. 6. The results are consistent with the binding of [3H]-mepyramine to intact U373 MG cells being to both plasma membrane and intracellular histamine H1-receptors. The high-affinity binding sensitive to the non-cell penetrant quaternary compounds and to temelastine is thus to plasma membrane H1-receptors. On exposure to 100 microM histamine receptors are translocated to the intracellular pool, since the change in the high-affinity binding of [3H]-mepyramine is primarily in the level of the pirdonium-insensitive binding, rather than in the total binding.

[Desensitization of the m3-muscarinic acetylcholine-receptor in the smooth muscle and the intracellular signal transduction]

Desensitization of the m3-muscarinic acetylcholine-receptor in the smooth muscle of the digestive tract is discussed together with the changes in intracellular signal transduction. Isolated single cells that show an all-or-none contractile response to acetylcholine were desensitized by treatment with 0.1 mM acetylcholine for 10 min, resulting in an increase in the threshold concentration of acetylcholine for contraction, but without changing any of the binding characteristics. Permeabilized cells showed that the desensitization is via uncoupling between the receptor and G-protein. Secretory cells (rat basophil leukemia-2H3 cells) transfected with human m3-receptor showed desensitization when treated with 0.1 mM carbachol for 30 min. The coupling between the receptor and G-protein was not impaired, but some unknown Ca(2+)-independent mechanism may be involved. Smooth muscle tissue was tested for its time-course of desensitization, and a novel transient resensitization was found at 1 min of incubation with 0.1 mM carbachol. This resensitization, and the desensitization prior to it, were accompanied with changes in binding affinity. However, the affinity was not changed, in parallel with desensitization afterwards, but the positive feedback loop of Ca(2+)-influx caused by alkalization via receptor-stimulation was suppressed. After a 30-min treatment, a Ca(2+)-independent mechanism caused the uncoupling and affinity decrease. Treatment for 3 hr increased the number of binding sites without recovery of the response. The desensitizing process is very diverse to achieve selectivity, but its purpose is in unity.

Significance of para-aortic lymph node dissection in patients with advanced and recurrent gastric cancer

Among 243 patients who underwent radical gastrectomy for advanced gastric cancer, 19 patients underwent radical gastrectomy with extended lymphadenectomy including cancer-positive para-aortic lymph nodes. Their prognosis was unexpectedly good, with a mean postoperative survival time of 24.1 months and a 2-year-survival rate of 42.4 percent. Another 4 patients developed para-aortic lymph node recurrence detected by computed tomographic scan during a follow-up examination. These 4 patients were treated with macroscopic curative dissection of the para-aortic lymph nodes. Although 2 of the 4 patients died within 6 months after re-operation, the prognosis of the other two patients was rather good when treated with active combination chemotherapy consisting of 5-fluorouracil, adriamycin and cisplatin. Dissection of para-aortic lymph nodes is considered of valuable in the treatment of advanced gastric cancer, and dissection of the para-aortic lymph node recurrence may also be valid when combined with potent chemotherapy.