[A case of ulcerative colitis with mesalazine intolerance complicated with agranulocytosis and septic shock during salazosulfapyridine administration]

A 73-year-old woman developed ulcerative colitis with mesalazine intolerance a year ago. She relapsed 10 months later. Although she was in clinical remission with salazosulfapyridine (SASP) and prednisolone administration, she developed agranulocytosis 53 days following SASP administration. She went into septic shock;however, she recovered with antibiotics, granulocyte colony-stimulating factor, and cardiotonic agents. Drug-induced lymphocyte stimulation test was positive for both mesalazine and SASP. Drug selection should be carefully determined in patients with 5-aminosalicylic acid intolerance.

Effect of nucleotide polymorphism in cis-regulatory and coding regions on amylase activity and fitness in Drosophila melanogaster

In natural populations of Drosophila melanogaster, there are many amylase (AMY) isozymes encoded by the duplicated genes, but their adaptive significance remains unclear. One approach to elucidate this issue is to understand the molecular basis of functional differences between the allelic classes. In this study, the effects of nucleotide polymorphism in 5'-flanking (cis-regulatory) and coding regions on AMY activity were examined, both on glucose and starch food media and in larvae and adults, using three chimeric Amylase (Amy) genes, Amy(c111), Amy(c161) and Amy(fc661). In this notation, the first number in the superscript indicates the sequence of the 5'-flnaking region (similar to Amy1 or Amy6), the second number refers to the coding region and the third number to the 3'-flanking region. We found that effect of nucleotide polymorphism in the coding region differed between larvae and adults. In larvae, the coding sequence of the Amy6 allele resulted in higher AMY activity than that of Amy1 allele, indicating the post-transcriptional differences between them. The cis-regulatory region derived from the Amy6 allele resulted in higher AMY activity in both larvae and adults. Thus, two fitness components, developmental time and productivity, were measured to examine whether polymorphism in the cis-regulatory region between the two alleles has an effect on them, but no significant difference was detected. We raise the implications for the evolution of subfunctionalization in multigene families.

Genetic coadaptation of the amylase gene system in Drosophila melanogaster: evidence for the selective advantage of the lowest AMY activity and of its epistatic genetic background

In natural populations of Drosophila melanogaster, an amylase isozyme with the lowest alpha-amylase activity (AMY(1,1)) is predominant. To evaluate the selective significance of AMY(1,1) and its regulatory factor(s), we examined selection experiments in laboratory populations on two distinct food environments. After 300 generations, AMY(1,1) became predominant (89%) in a glucose (a product of AMY)-rich environment, while an isozyme with higher alpha-amylase activity, AMY(1,6), became predominant (83%) in a starch (substrate)-rich environment. We found that the identical alleles of the amylase (Amy) gene, which encodes each of AMY(1,1) and AMY(1,6), were shared between the two populations in the different food environments, employing the nucleotide sequencing of the duplicated Amy genes. Nevertheless, AMY(1,6) homozygotes selected in the starch-rich environment had a twofold higher AMY enzyme activity than those selected in the glucose-rich environment, suggesting a coadaptation of the coding region and its regulatory factor(s) on the genetic background. Such a difference in AMY enzyme activity was not detected between AMY(1,1) homozygotes, suggesting that the effect of the genetic background is epistatic. Our results indicate that natural selection is working on the Amy gene system as a whole for flies to adapt to the various food environments of local populations.

Autoimmune vesicles on the face and neck. A variant of Brunsting-Perry type localized bullous pemphigoid?

We report a case of blistering disease presenting a unique distribution of vesiculobullous lesions on the face and neck which is similar to Brunsting-Perry type of localized bullous pemphigoid (BP). Histopathology of a lesional skin biopsy demonstrated a subepidermal blister. Direct immunofluorescence demonstrated a strong linear deposition of IgG and IgA to the basement membrane zone, and a faint staining for C3. However, circulating antibodies were not detected by indirect immunofluorescence and immunoblotting. And the patient did not develop atrophic scars and was a relatively young woman. This case might be a variant of Brunsting-Perry type of localized BP or localized epidermolysis bullosa acquisita, presenting the clinical heterogeneity of subepidermal blistering diseases.

Receptors for the carboxyl-terminal region of pth(1-84) are highly expressed in osteocytic cells

PTH is a potent systemic regulator of cellular differentiation and function in bone. It acts upon cells of the osteoblastic lineage via the G protein-coupled type-1 PTH/PTH-related peptide receptor (PTH1R). Carboxyl fragments of intact PTH(1-84) (C-PTH fragments) are cosecreted with it by the parathyroid glands in a calcium-dependent manner and also are generated via proteolysis of the hormone in peripheral tissues. Receptors that recognize C-PTH fragments (CPTHRs) have been described previously in osteoblastic and chondrocytic cells. To directly study CPTHRs in bone cells, we isolated clonal, conditionally transformed cell lines from fetal calvarial bone of mice that are homozygous for targeted ablation of the PTH1R gene and transgenically express a temperature-sensitive mutant SV40 T antigen. Cells with the highest specific binding of the CPTHR radioligand (125)I-[Tyr(34)]hPTH(19-84) exhibited a stellate, dendritic appearance suggestive of an osteocytic phenotype and expressed 6- to 10-fold more CPTHR sites/cell than did osteoblastic cells previously isolated from the same bones. In these osteocytic (OC) cells, expression of mRNAs for CD44, connexin 43, and osteocalcin was high, whereas that for alkaline phosphatase and cbfa-1/osf-2 was negligible. The CPTHR radioligand was displaced completely by hPTH(1-84), hPTH(19-84) and hPTH(24-84) (IC(50)s = 20-50 nM) and by hPTH(39-84) (IC(50) = 500 nM) but only minimally (24%) by 10,000 nM hPTH(1-34). CPTHR binding was down-regulated dose dependently by hPTH(1-84), an effect mimicked by ionomycin and active phorbol ester. Human PTH(1-84) and hPTH(39-84) altered connexin 43 expression and increased apoptosis in OC cells. Apoptosis induced by PTH(1-84) was blocked by the caspase inhibitor DEVD. We conclude that osteocytes, the most abundant cells in bone, may be principal target cells for unique actions of intact PTH(1-84) and circulating PTH C-fragments that are mediated by CPTHRs.

Molecular evolution of duplicated amylase gene regions in Drosophila melanogaster: evidence of positive selection in the coding regions and selective constraints in the cis-regulatory regions

In this study, we randomly sampled Drosophila melanogaster from Japanese and Kenyan natural populations. We sequenced duplicated (proximal and distal) Amy gene regions to test whether the patterns of polymorphism were consistent with neutral molecular evolution. F(st) between the two geographically distant populations, estimated from Amy gene regions, was 0.084, smaller than reported values for other loci, comparing African and Asian populations. Furthermore, little genetic differentiation was found at a microsatellite locus (DROYANETSB) in these samples (G'st = -0.018). The results of several tests (Tajima's, Fu and Li's, and Wall's tests) were not significantly different from neutrality. However, a significantly higher level of fixed replacement substitutions was detected by a modified McDonald and Kreitman test for both populations. This indicates that positive selection occurred during or immediately after the speciation of D. melanogaster. Sliding-window analysis showed that the proximal region 1, a part of the proximal 5' flanking region, was conserved between D. melanogaster and its sibling species, D. simulans. An HKA test was significant when the proximal region 1 was compared with the 5' flanking region of Alcohol dehydrogenase (Adh), indicating a severe selective constraint on the Amy proximal region 1. These results suggest that natural selection has played an important role in the molecular evolution of Amy gene regions in D. melanogaster.

Ghrelin stimulates gastric acid secretion and motility in rats

Ghrelin, a novel growth-hormone-releasing peptide, was discovered in rat and human stomach tissues. However, its physiological and pharmacological actions in the gastric function remain to be determined. Therefore, we studied the effects of rat ghrelin on gastric functions in urethane-anesthetized rats. Intravenous administrations of rat ghrelin at 0.8 to 20 microgram/kg dose-dependently increased not only gastric acid secretion measured by a lumen-perfused method, but also gastric motility measured by a miniature balloon method. The maximum response in gastric acid secretion was almost equipotent to that of histamine (3 mg/kg, i.v.). Moreover, these actions were abolished by pretreatment with either atropine (1 mg/kg, s.c.) or bilateral cervical vagotomy, but not by a histamine H(2)-receptor antagonist (famotidine, 1 mg/kg, s.c.). These results taken together suggest that ghrelin may play a physiological role in the vagal control of gastric function in rats.

Studies on antihypertensive agents with antithrombotic activity. 2. Syntheses and pharmacological evaluation of pyrrolo[2,3-c]azepine derivatives

As an extension of our previous investigation, a series of 7-aminoalkylpyrrolo[2,3-c]azepine derivatives was synthesized and evaluated as alpha1-adrenergic- and serotonin 2 (5-HT2)-receptor antagonists, with the aim of finding a novel potent antihypertensive agent with both activities. Among the compounds obtained in this study, (E)-1-ethyl-7-[3-[4-(4-fluorophenyl)piperazin-1-yl]propyl]-4-hy droxyimino-1,4,5,6,7,8-hexahydropyrrolo[2,3-c]azepin-8-on e (16d) displayed potent alpha1-adrenoceptor blocking activity (pA2=7.83+/-0.20) and 5-HT2-receptor blocking activity (pA2=9.47+/-0.17) in isolated guinea pig arteries. At 3 mg/kg oral administration, compound 16d exhibited antihypertensive activity more potent than that of doxazosin in deoxycorticosterone acetate (DOCA)-salt hypertensive dogs. Furthermore, this compound reduced the rate of mouse acute pulmonary thromboembolytic death induced by collagen and serotonin at oral doses of 0.3 mg/kg or more, and its effect lasted for at least 6 h at 3 mg/kg.

Autoantibodies against oxidized low-density lipoprotein correlate with Achilles tendon xanthomas

Although there is increasing evidence for anti-oxidized low-densitiy lipoprotein (LDL) autoantibodies in human sera, their diagnostic utility remains controversial. We examined the difference in autoantibody titers between patients with Achilles tendon xanthoma and control subjects. Fifteen hyperlipidemic patients with Achilles tendon xanthoma (group A+) and 94 hyperlipidemic patients without Achilles tendon xanthoma (group A-) were studied. Quantification of anti-oxidized LDL and anti-native LDL autoantibodies was performed using an ELISA method. To calculate antibody titers, we used the ratio between the spectrophotometric reading of anti-oxidized LDL and anti-native LDL wells. Using oxidized LDL that was purified by gel-permeation chromatography as antigen, immunoglobulin G level differed significantly between groups A+ and A- (p < 0.01). In contrast, using native and oxidized LDL as antigens without chromatographical purification revealed no significant difference between the two groups. Furthermore, immunoglobulin autoantibody titer did not correlate with age, body mass index, total cholesterol, high-density lipoprotein cholesterol, LDL cholesterol, or triglyceride in the entire group of subjects. Thus, immunoglobulin G autoantibody values appear to correlate with Achilles tendon xanthoma.

[Antiarrhythmic effects of pilsicainide hydrochloride and effects on cardiac function and ECG in dogs: comparison with disopyramide]

Antiarrhythmic effects and cardiovascular effects of pilsicainide hydrochloride were compared with those of disopyramide in a canine model of coronary ligation-induced ventricular arrhythmias and anesthetized dogs. Pilsicainide (1.25, 2.5 and 5 mg/kg) and disopyramide (2.5 and 5 mg/kg) decreased the arrhythmic ratio ¿(ventricular arrhythmias/total heart rate) x 100¿ dose-dependently. Pilsicainide at 2.5 and 5 mg/kg and disopyramide at 5 mg/kg suppressed ventricular arrhythmias more than 50%. The effective dose of pilsicainide was lower than that of disopyramide, but the effective plasma concentration of pilsicainide was between 3 and 8 micrograms/ml, which was almost the same as that of disopyramide. In anesthetized dogs, both drugs decreased LV dP/dt max in almost the same concentration-dependent manner. PQ-interval was prolonged by pilsicainide, but not by disopyramide. QRS and QTc were prolonged by both drugs in a concentration-dependent manner. However, the prolongation of QTc by disopyramide was provoked at lower plasma concentrations than by pilsicainide. Because the excessive prolongation of QTc lead to the lethal arrhythmias such as torsades de pointes, pilsicainide may be useful as an injectable antiarrhythmic agent superior to disopyramide.

Synthesis and serotonin 2 (5-HT2) receptor antagonist activity of 5-aminoalkyl-substituted pyrrolo[3,2-c]azepines and related compounds

A series of 5-aminoalkylpyrrolo[3,2-c]azepine derivatives was synthesized and their serotonin 2 (5-HT2) receptor antagonist and antiplatelet aggregation activities were evaluated. 5-HT2 receptor antagonist activity was largely determined by the nature of the substituent at the 8-position as well as the aminoalkyl group at the 5-position of the pyrrolo[3,2-c]azepine ring. Compound 18a, 5-[3-[4-(4-fluorophenyl)piperazin-1-yl]propyl]-8-hydroxy-1-methyl- 1,4,5,6,7,8-hexahydropyrrolo[3,2-c]azepin-4-one, was recognized as having potent 5-HT2 receptor antagonist activity with weak alpha1 adrenoceptor blocking activity and no significant D2 receptor binding affinity, while the corresponding isomeric pyrrolo[3,4-c]azepine derivative (22) displayed only weak 5-HT2 receptor antagonist activity. After racemic 18a was resolved directly via diastereomeric salt formation, each enantiomer was evaluated precisely. The 5-HT2 receptor antagonist activity of 18a was found to reside primarily in (-)-18a (which was about 14-fold more potent than (+)-18a in isolated guinea pig arteries). Consequently, (S)-(-)-18a (SUN C5174) displayed the overall best profile with potent 5-HT2 receptor antagonist activity (pA2=8.98+/-0.06) and high selectivity versus other receptors. SUN C5174 showed a marked inhibitory effect on the platelet aggregation induced by serotonin in combination with collagen and adenosine diphosphate (ADP) in canine or human platelet-rich plasma (IC50=6.5 to 16 nM). Moreover, this compound significantly inhibited the mortality rate in mouse acute pulmonary thromboembolytic death induced by collagen and serotonin at oral doses of 0.3 mg/kg or higher. SUN C5174 is currently undergoing clinical evaluation.

Evolution of nucleotide substitutions and gene regulation in the amylase multigenes in Drosophila kikkawai and its sibling species

In order to determine evolutionary changes in gene regulation and the nucleotide substitution pattern in a multigene family, the amylase multigenes were characterized in Drosophila kikkawai and its sibling species. The nucleotide substitution pattern was investigated. Drosophila kikkawai has four amylase genes. The Amy1 and Amy2 genes are a head-to-head duplication in the middle of the B arm of the second chromosome, while the Amy3 and Amy4 genes are a tail-to-tail duplication near the centromere of the same chromosome. In the sibling species of D. kikkawai (Drosophila bocki, Drosophila leontia, and Drosophila lini), sequencing of the Amy1, Amy2, Amy3, and Amy4 genes revealed that the Amy1 and Amy2 gene group diverged from Amy3 and Amy4 after duplication. In the Amy1 and Amy2 genes, the divergent evolution occurred in the flanking regions; in contrast, the coding regions have evolved in concerted fashion. The electrophoretic pattern of AMY isozymes was also examined. In D. kikkawai and its siblings, two or three electrophoretically different isozymes are encoded by the Amy1 and Amy2 genes (S isozyme) and by the Amy3 and Amy4 genes (F (M) isozymes). The S and F (M) isozymes show different patterns of band intensity when larvae and flies were fed in different media. Amy1 and Amy2, which encode the S isozyme, are more strikingly regulated than Amy3 and Amy4, which encode the F (M) isozyme. The GC content and codon usage bias were higher for the Amy1 and Amy2 genes than for the Amy3 and Amy4 genes. Although the ratio of synonymous and replacement substitutions within the Amy1 and Amy2 gene group was not significantly different from that within the Amy3 and Amy4 gene group, the synonymous substitution rate in the lineage of Amy1 and Amy2 was lower than that of Amy3 and Amy4. In conclusion, after the first duplication but before speciation of four species, the synonymous substitution rate between the two lineages and the electrophoretic pattern of the isozymes encoded by them changed, although we do not know whether there was any evolutionary relationship between the two.

Effect of human plasma-type platelet-activating factor acetylhydrolase in two anaphylactic shock models

The effect of human recombinant plasma-type platelet-activating factor (PAF) acetylhydrolase was examined in two murine models, PAF-induced death and active anaphylactic models. In the PAF-induced death model where mice were injected intravenously with 40 microg/kg of PAF, the administration of PAF acetylhydrolase reduced mortality in a dose-dependent manner, showing complete prevention of mortality at 1.0 mg/kg. Myeloperoxidase activity, the marker for neutrophils, was increased in the lung by PAF injection, and the PAF acetylhydrolase treatment significantly reversed the increase in myeloperoxidase activity. As in the PAF-induced model, PAF acetylhydrolase also decreased mortality in the active anaphylactic shock model where bovine serum albumin was injected intravenously to mice previously immunized with bovine serum albumin. The protective effect of PAF acetylhydrolase on mortality in this model was significant at 1.0 mg/kg. These results suggest that PAF is an important mediator in the lethality of systemic anaphylaxis, and that PAF acetylhydrolase may be beneficial for treatment of anaphylactic shock.

Sweet's syndrome with gastric cancer

Solid tumors are found in about 15% of malignancy-associated Sweet's syndrome, but only 3 cases of Sweet's syndrome with gastric cancer have been reported. We describe a 59-year-old Japanese man with gastric cancer associated with Sweet's syndrome.

Evolution of the amylase isozymes in the Drosophila melanogaster species subgroup

The relationship between the net charge of molecules and their mobility on electrophoresis was analyzed for Drosophila alpha-amylases. Most of the differences in electrophoretic mobility, 98.2%, can be explained by the charge state. Therefore five reference amino acid sites, which are informative residues for charge differences among amylase isozymes, were considered for the evolution of the isozymes in Drosophila melanogaster. The amylase isozymes in D. melanogaster can be classified into three groups, I (AMY1, AMY2, and AMY3-A), II (AMY3-B and AMY4), and III (AMY5, AMY6-A, and AMY6-B), based on the differences in the reference sites. The most primitive amylase in D. melanogaster was found to belong to Group I, most likely the AMY2 isozyme. Groups II and III could have been derived from Group I. These results were confirmed by the analysis of 38 amino acid sites with charge differences in Drosophila.

Synthesis and pharmacological evaluation of pyrroloazepine derivatives as potent antihypertensive agents with antiplatelet aggregation activity

A series of 1-aminoalkyl-pyrrolo[2,3-c]azepin-8-one derivatives was synthesized and evaluated as alpha 1 adrenergic and serotonin 2 (5-HT2) receptor antagonists, with the aim of finding a novel antihypertensive agent potently exhibiting both activities. Some compounds with a 4-[4-(4-fluorobenzoyl)piperidino]butyl group at the 1-position exhibited both activities, and varied significantly in terms of the substituents at the 4-position of the pyrroloazepine ring. Among the compounds obtained in this study, (E)-1-[4-[4-(4-fluorobenzoyl)piperidino]-butyl]-4-hydroxyimino-7- methyl-1,4,5,6,7,8-hexahydropyrrolo[2,3-c]azepin-8-one (15a, SUN9221) displayed potent alpha 1-adrenergic antagonistic activity (pA2 = 8.89 +/- 0.21) and 5-HT2 antagonistic activity (pA2 = 8.74 +/- 0.22) in isolated guinea pig arteries. This compound exhibited antihypertensive activity and a duration of action equivalent to orally administered prazosin or doxazosin, 3 mg/kg, in conscious spontaneously hypertensive rats, as well as potent antiplatelet aggregation activity.

[Isoproterenol continuous nebulization of childhood status asthmaticus. II. Efficacy and side effects of low-dose method comparing with high-dose method]

We investigated the efficacy and side effects of "low-dose isoproterenol continuous nebulization" for childhood status asthmaticus, and compared them with those of "high-dose method". "Low-dose" is defined as 10 ml or less of 0.5% dl-isoproterenol solution diluted in 500 ml of normal saline. Subjects were 23 children who were hospitalized and underwent the nebulization therapy. The period of continuous nebulization was 26.3 +/- 12.5 hours. The Wood's clinical score clearly decreased in 22 cases, the average score changing from 7.3 +/- 1.2 to 2.8 +/- 1.5. Heart rate was not elevated significantly during the nebulization period, and decreased gradually (142 +/- 22/min at the start of the nebulization, 145 +/- 22/min at 1 hour, and 134 +/- 23/min at 3 hours, and 103 +/- 13/min at the cessation of the nebulization). Serum GOT, LDH, CPK, and potassium were decreased after the nebulization compared with the values before the treatment, the changes of the last 2 items being statistically significant. Two subjects who had vomited before the nebulization therapy complained nausea during the procedure, and one experienced transient finger tremor. We conclude that "low-dose isoproterenol continuous nebulization" is an effective and safe method for childhood status asthmaticus. We expect that this method will be familiar to all clinicians.

Cardiac-specific overexpression of angiotensin II AT2 receptor causes attenuated response to AT1 receptor-mediated pressor and chronotropic effects

Angiotensin (Ang) II has two major receptor isoforms, AT1 and AT2. Currently, AT1 antagonists are undergoing clinical trials in patients with cardiovascular diseases. Treatment with AT1 antagonists causes elevation of plasma Ang II which selectively binds to AT2 and exerts as yet undefined effects. Cardiac AT2 level is low in adult hearts, whereas its distribution ratio is increased during cardiac remodeling and its action is enhanced by application of AT1 antagonists. Although in AT2 knock-out mice sensitivity to the pressor action of Ang II was increased, underlying mechanisms remain undefined. Here, we report the unexpected finding that cardiac-specific overexpression of the AT2 gene using alpha-myosin heavy chain promoter resulted in decreased sensitivity to AT1-mediated pressor and chronotropic actions. AT2 protein undetectable in the hearts of wild-type mice was overexpressed in atria and ventricles of the AT2 transgenic (TG) mice and the proportions of AT2 relative to AT1 were 41% in atria and 45% in ventricles. No obvious morphological change was observed in the myocardium and there was no significant difference in cardiac development or heart to body weight ratio between wild-type and TG mice. Infusion of Ang II to AT2 TG mice caused a significantly attenuated increase in blood pressure response and the change was completely blocked by pretreatment with AT2 antagonist. This decreased sensitivity to Ang II-induced pressor action was mainly due to the AT2-mediated strong negative chronotropic effect and exerted by circulating Ang II in a physiological range that did not stimulate catecholamine release. Isolated hearts of AT2 transgenic mice perfused using a Langendorff apparatus also showed decreased chronotropic responses to Ang II with no effects on left ventricular dp/dt max values, and Ang II-induced activity of mitogen-activated protein kinase was inhibited in left ventricles in the transgenic mice. Although transient outward K+ current recorded in cardiomyocytes from AT2 TG mice was not influenced by AT2 activation, this study suggested that overexpression of AT2 decreases the sensitivity of pacemaker cells to Ang II. Our results demonstrate that stimulation of cardia AT2 exerts a novel antipressor action by inhibiting AT1-mediated chronotropic effects, and that application of AT1 antagonists to patients with cardiovascular diseases has beneficial pharmacotherapeutic effects of stimulating cardiac AT2.

Protective effects of polysaccharide fucoidin on myocardial ischemia-reperfusion injury in rats

We tested whether polysaccharide fucoidin, which inhibits leukocyte rolling in the mesenteric venule, has protective effects in the rat myocardial 30-min ischemia and 6-h reperfusion injury model. Intravenous infusion of fucoidin (27 microg/kg/min from 10 min before to 6 h after reperfusion) significantly attenuated myocardial infarct size 6 h after reperfusion. In this ischemia and reperfusion heart model, expression of P-selectin (determined immunohistochemically) was observed on the venular endothelial cells in the heart 30 min after reperfusion and also was sustained after 6 h. Neutrophil infiltration as estimated by myeloperoxidase activity significantly increased 2 h after reperfusion and kept increasing with time until 6 h after reperfusion. Four-hour infusion of fucoidin after reperfusion significantly reduced neutrophil infiltration, whereas the 2-h infusion of fucoidin did not. These results indicate that neutrophil infiltration and myocardial injury are attributed to expression of P-selectin after reperfusion, and that one of the inhibitory mechanisms of fucoidin seems to be blockade of P-selectin-mediated neutrophil rolling on the vessel wall.

Molecular evolution of the Amy multigenes in the subgenus Sophophora of Drosophila

Molecular evolution of the Amy multigenes in Drosophila was investigated using PCR amplification. Twenty-five partial Amy sequences from 13 species belonging mainly to the subgenus Sophophora were determine, and a molecular phylogeny of the Amy genes in Drosophila was constructed, together with published Amy sequences. Clustering of species are mostly consistent with the traditional classification and that inferred from other genes. From sequence divergence between PCR products, several species, including D. elegans and D. fuyamai, were suggested to have multiple copies of the Amy genes. The loss of an intron took place at least three times after the Sophophora radiation. In order to investigate the mechanism of sequence evolution, the numbers of amino acid replacement and synonymous substitutions in five lineages were estimated. The heterogeneity in the relative numbers of synonymous and replacement substitutions among the lineages was found. Possible roles of selection in the sequence evolution of the Amy gene are discussed.

The 69-84 amino acid region of the parathyroid hormone molecule is essential for the interaction of the hormone with the binding sites with carboxyl-terminal specificity

We evaluated the competitive inhibitory effect of intact PTH, the amino-terminal PTH(1-34) fragment, and a series of truncated carboxyl-terminal PTH fragments on the binding of internally 35S-labeled human PTH(1-84) ([35S]hPTH(1-84)) to osteoblastic cells (ROS 17/2.8), in order to identify the minimum and critical elements within the PTH molecule for the interaction with the binding sites specific for the carboxyl-terminal region of the hormone. When the amino-terminal region of the PTH molecule was truncated stepwise, hPTH(35-84), hPTH(53-84) and hPTH(69-84), but not hPTH(70-84), significantly inhibited the [35S]hPTH(1-84) binding. On the other hand, the simple deletion of the carboxyl-terminal glutamine at position 84 of hPTH(53-84) [hPTH(53-83)] resulted in blunting the inhibitory effect of the peptide on the [35S]hPTH(1-84) binding. Furthermore, hPTH(35-84), hPTH(53-84) and hPTH(69-84), but not hPTH(70-84) nor hPTH(53-83), augmented the inhibitory effect of the amino-terminal PTH fragment [hPTH(1-34)] on the [35S]hPTH(1-84) binding. Of special interest was that the combination of hPTH(1-34) and hPTH(35-84) reproduced the inhibitory effect of unlabeled hPTH(1-84) on the [35S]hPTH(1-84) binding, on an equimolar basis. The 69-84 region of the PTH molecule thus appears to be crucial for binding to the carboxyl-terminal specific binding sites for PTH in osteoblasts. The interaction of the amino-terminal and carboxyl-terminal regions of a PTH molecule with their own respective binding sites seemed to occur in a fairly independent manner.

Evolution of the response patterns to dietary carbohydrates and the developmental differentiation of gene expression of alpha-amylase in Drosophila

Intraspecific variation of alpha-amylase activity in D. melanogaster and D. immigrans, which is distantly related to D. melanogaster, and interspecific variation of alpha-amylase activity in 18 Drosophila species were examined. The amount of intraspecific variation of alpha-amylase activities measured in terms of coefficient of variation in D. melanogaster and D. immigrans was one-half and one-tenth or less, respectively, of the interspecific variation in 18 Drosophila species. We also surveyed the response patterns of alpha-amylase activity to dietary carbohydrates at the larval and adult stages. The levels of alpha-amylase activity depended on both repression by dietary glucose (glucose repression) and induction by dietary starch (starch induction). In general, our data suggest that glucose repression was conserved among species at both stages while starch induction was mainly observed in larvae, although the degree of the response depended on species. In D. lebanonensis lebanonensis and D. serrata, larvae expressed electrophoretically different alpha-amylase variants (isozymes) from those of adult flies. These results may suggest that the regulatory systems responsible both for the response to environment and developmental expression are different among species in Drosophila.

Characterization of a novel parathyroid hormone (PTH) receptor with specificity for the carboxyl-terminal region of PTH-(1-84)

Carboxyl-terminal fragments of PTH (C-PTH) appear to have biological properties different from those mediated by the amino-terminal portions of PTH and PTH-related peptide (PTHrP). To characterize a C-PTH receptor that may be involved in mediating these functions, we performed RRAs and affinity cross-linking studies with several clonal cell lines. Radiolabeled recombinant [Leu8,18,Tyr34]human PTH-(1-84)[mutPTH-(1-84) and [Tyr34] human PTH-(19-84)[mutPTH-(19-84) showed little or no specific binding to stably expressed recombinant PTH/PTHrP receptors. However, high affinity binding was observed using osteoblast-like and rat parathyroid (PT-r3) cells. The apparent Kd values were 20-30 nM for PTH-(1-84), mutPTH-(1-84), and mutPTH-(19-84), respectively; 400-800 nM for PTH-(39-84); and more than 5000 nM for PTH-(53-84). [Nle8,18,Tyr34]bovine PTH-(1-34)amide [PTH-(1-34)], PTH-(44-68), PTHrP-(37-74), and PTHrP-(109-141) showed no displacement of either radioligand. C-PTH receptor number was increased up to 2-fold by pretreating ROS 17/2.8 cells with increasing doses of PTH-(1-34), PTH-(1-84), or 8-bromo-cAMP, whereas no change was observed in response to dexamethasone or PTH-(39-84). Cross-linking studies using radiolabeled mutPTH-(1-84) or mutPTH-(19-84) revealed specific labeling of two proteins in ROS 17/2.8 cells that were approximately 40 and 90 kilodaltons in size (including the radioligand of approximately 10 kilodaltons). The intensity of affinity labeling of both proteins was dose dependently inhibited by increasing concentrations of unlabeled PTH-(1-84) and several carboxyl-terminal PTH-(1-84) fragments, but not by PTH-(1-34). Similar studies with PT-r3 cells revealed only a single protein band of about 90 kilodaltons. These data indicate that the carboxyl-terminal portion of PTH-(1-84) binds specifically to a unique receptor/binding protein distinct from the previously isolated PTH/PTHrP receptor.

Evolutionary relationships and sequence variation of alpha-amylase variants encoded by duplicated genes in the Amy locus of Drosophila melanogaster

To infer the genealogical relationships of alpha-amylase electromorphs of Drosophila melanogaster, we determined the nucleotide sequences of a collection of electromorphs sampled throughout the world. On average there were 1.0 amino acid substitutions between identical electromorphs and 3.9 between different electromorphs, respectively. We found that the evolution of AMY1 through AMY6 electromorphs occurred by sequential accumulation of single amino acid substitutions each causing one charge difference. The nucleotide diversities at synonymous sites within Amy1,Amy2,Amy3,Amy4 and Amy6 were 0.0321, 0.0000, 0.0355, 0.0059 and 0.0030, respectively. We also obtained evidence of genetic exchanges, such as intrachromosomal recombination, interchromosomal recombination or gene conversion, between the two duplicated Amy genes as well as among the alleles.

Intergeneric hybridization between Brassica napus and Sinapis pubescens, and the cytology and crossability of their progenies

The cytological possibility of gene transfer from Sinapis pubescens to Brassica napus was investigated. Intergeneric hybrids between Brassica napus (2n = 38) and Sinapis pubescens (2n = 18) were produced through ovary culture. The F1 hybrids were dihaploid and the chromosome configurations were (0-1) III + (2-11) II + (5-24) I . One F2 plant with 38 chromosomes was obtained from open pollination of the F1 hybrid. Thirty-one seeds were obtained from the backcross of the F2 plant with B. napus. Five out of seven plants had 38 chromosomes, and the pollen stainability ranged from 0% to 81.4%. In the B2 plants obtained from the backcross of B1 plants with B. napus, 66.7% of the plants examined had 38 chromosomes. S. pubescens may become a gene source for the improvement of B. napus.

[Effect of carperitide (alpha-human atrial natriuretic polypeptide) on the cardiovascular system in experimental animals]

The cardiovascular and diuretic actions of carperitide were studied in experimental animals. Carperitide relaxed various canine arteries and veins that were contracted by high K+ or norepinephrine. Carperitide stimulated particulate guanylate cyclase from rat thoracic aortas. Carperitide had almost no effect on coronary perfusion pressure or heart rate, but caused a slight decrease in contractile force in isolated guinea pig hearts. Carperitide tended to decrease isoproterenol-induced renin release from isolated rat kidney slices and elicited decreases in angiotensin II-induced aldosterone release from bovine zona glomerulosa cells. Intravenous injection of carperitide elicited decreases in arterial blood pressure and total peripheral resistance in the anesthetized and conscious dogs. Carperitide also elicited transient increases in cardiac output and coronary blood flow followed by slight decreases in them. Intravenous infusion of carperitide elicited decreases in pulmonary capillary wedge pressure, pulmonary pressure and right atrial pressure in association with elevating plasma carperitide (ANP like immuno-reactivity) level in dogs with heart failure induced by coronary artery occlusion and saline loading. These results suggest that carperitide decreases both preload and afterload and can improve the untoward hemodynamic alterations in animals with acute experimental heart failure.

Low neurotoxicity of LJC 10,627, a novel 1 beta-methyl carbapenem antibiotic: inhibition of gamma-aminobutyric acidA, benzodiazepine, and glycine receptor binding in relation to lack of central nervous system toxicity in rats

The toxicity of LJC 10,627 to the central nervous system of rats was evaluated by examining the effects of the compound on gamma-aminobutyric acidA, benzodiazepine, and glycine receptor binding in rat synaptic membranes and on the induction of behavioral convulsions by intraventricular administration to rats. The concentrations of this compound needed to inhibit specific [3H]muscimol binding, specific [3H]diazepam binding, and specific [3H]strychnine binding were greater than those of imipenem, as demonstrated by the 50% inhibitory concentrations (IC50S of LJC 10,627, greater than 10 mM for each; IC50S of imipenem, 0.6, 1.9, and 0.2 mM, respectively). These results reflect the fact that LJC 10,627 does not evoke severe convulsions or cause death, even when it is administered intraventricularly at a high dose (300 micrograms per rat), and suggest that the low neurotoxic potential of LJC 10,627 may be attributed to the chemical structure of this compound, which has a methyl radical at the 1 beta site and a triazolium radical at the side chain of the second site.

Antiarrhythmic agents act differently on the activation phase of the ACh-response in guinea-pig atrial myocytes

1. Anti-acetylcholine effects of pilsicainide, flecainide, disopyramide and propafenone on the acetylcholine (ACh)-induced K+ current (IK.ACh) were examined in dissociated guinea-pig atrial myocytes under whole-cell voltage clamp by the use of the 'concentration-clamp' technique. 2. The IK.ACh was activated with a latency of about 100 ms after 1 microM ACh application and desensitized to a steady-state level. The latent period and the time to peak response were shortened with increasing ACh concentration. 3. The values of half-maximal inhibition (IC50) on the peak and steady state responses were 25 and 25 microM for pilsicainide, 1.7 and 2.0 microM for disopyramide, 19 and 2.0 microM for flecainide and 0.7 and 0.2 microM for propafenone, respectively. 4. Pilsicainide and disopyramide increased the latent period and the time to peak of IK.ACh in a concentration-dependent manner. Flecainide and propafenone did not change the latent period, but shortened the time to peak and hastened the decay of IK.ACh in a voltage-independent manner. 5. The results suggest that the mechanisms underlying the anti-acetylcholine effect of antiarrhythmic drugs are different among these drugs: i.e., pilsicainide and disopyramide mainly block the muscarinic ACh receptors while flecainide and propafenone inhibit the K+ channel itself as open channel blockers.

Modes of the Na channel blocking action of pilsicainide, a new antiarrhythmic agent, in cardiac cells

Using a whole cell clamp technique, the blockade of sodium currents (INa) by pilsicainide, a new antiarrhythmic agent, applied either intracellularly or extracellularly, was studied in single myocytes isolated from guinea pig right ventricle. Pilsicainide applied extracellularly inhibited the peak amplitude of INa in concentration- (from 10(-5) M to 10(-4) M) and rate- (from 0.5 Hz to 3.0 Hz) dependent manners. The onset rate of the blockade in INa was almost constant, independent of frequency of stimulus, but higher at high concentration of pilsicainide. The time constant in the recovery phase from INa inactivation remained almost constant (65 to 75 msec) in the range of concentrations used. Similar results were obtained by intracellular application of 10(-3) M pilsicainide. Pilsicainide applied intracellularly inhibited INa in a rate-dependent manner. The blocking potency of internally applied pilsicainide almost corresponded to that of external 10(-5) M pilsicainide. The onset rate of INa inactivation (from 0.098/pulse to 0.130/pulse) and the recovery time constant (77 msec) was similar to those of external 10(-5) M pilsicainide. These results suggest that pilsicainide, irrespective of intra- or extracellular application, shares a common binding site to block INa in cardiac myocytes.

Effects of ethyl 4-chloro-2-methylphenoxyacetate on bile composition in golden hamsters

The effects of ethyl 4-chloro-2-methylphenoxyacetate (MCPA) on the cholesterol levels in the liver, serum and gallbladder bile, the composition of both biliary lipids and bile acids, and the hepatic enzyme activities relating to the bile acid formation were investigated in male golden hamsters. MCPA was administered orally to the animals at the doses of 200, 500 and 1,000 mg/kg/day for 2 weeks. Clofibrate (500 mg/kg/day) was also tested for comparison, because of its similarity to MCPA in chemical structure and pharmacological actions. Body weight gain was slightly decreased, but liver to body weight ratio was increased in the MCPA groups of 500 and 1,000 mg/kg and also in the clofibrate group. In these groups, the cholesterol level in the liver was decreased but that in bile was increased. The composition of biliary bile acids was also changed in both the MCPA groups (500 and 1,000 mg/kg) and the clofibrate group, but in a different manner; the levels and proportions of secondary bile acids were increased in the MCPA groups, while those of cholic acid and deoxycholic acid were decreased in the clofibrate group. These results indicate that MCPA and clofibrate may affect cholesterol catabolism differently, although these two compounds contain the same chlorinated phenoxy acid moiety. The increased level of cholesterol in bile might lead to the formation of cholesterol gallstone, which is frequently found in patients with gallbladder cancer. It is inferred that exposure to MCPA could be a risk factor for gallbladder cancer, which was initiated with some chemical carcinogens, because it increased the levels and proportions of both cholesterol and secondary bile acids in bile.

Mechanisms of the anticholinergic effect of SUN 1165 in comparison with flecainide, disopyramide and quinidine in single atrial myocytes isolated from guinea-pig

1. The mechanism of the anticholinergic effect of SUN 1165 on the acetylcholine (ACh)-induced K+ current (IK.ACh) was examined and compared with those of flecainide, disopyramide and quinidine in single atrial myocytes, in a whole-cell configuration by use of the concentration-jump technique. This technique combines an intracellular perfusion and a rapid exchange of external solution surrounding the voltage-clamped single myocyte within 2 ms. 2. In the cells loaded with guanosine-5'-triphosphate (GTP), 100 microM, the muscarinic ACh response, (IK.ACh), was mediated by GTP-binding proteins. The concentrations of the test drugs that produced a half-maximal inhibition of ACh (1 microM)-induced IK.ACh (IC50) were 29 microM for SUN 1165, 3.6 microM for flecainide, 1.7 microM for disopyramide, and 1.6 microM for quinidine. The blockade of IK.ACh by SUN 1165 and its recovery from the inhibition occurred within a few seconds. Disopyramide had a similar rapid action, while the effects of flecainide and quinidine occurred much more slowly within a few tens of seconds. 3. In cells loaded with 100 microM guanosine-5'-O-(3-thiotriphosphate) (GTP gamma S, a nonhydrolysable GTP analogue), the K+ channel was uncoupled from the muscarinic receptors and activated irreversibly due to direct activation of GTP-binding proteins by GTP gamma S. SUN 1165 and disopyramide had a weak inhibitory effect (IC50 greater than 100 microM for both), while flecainide and quinidine depressed the GTP gamma S-induced K+ current with similar potencies to the cases of ACh-induced currents; IC50 was 5.3 microM for flecainide and 4.4 microM for quinidine. 4 These results suggest that the mechanisms underlying the anticholinergic effects of these antiarrhythmic drugs are different; disopyramide and high concentrations of SUN 1165 mainly block muscarinic ACh receptors in atrial myocytes, while flecainide and quinidine inhibit the K+ channel itself and/or GTP-binding proteins.

Effects of MCPA and other phenoxyacid compounds on hepatic xenobiotic metabolism in rats

The effects of ethyl 4-chloro-2-methylphenoxyacetate (MCPA) and other phenoxyacid compounds on hepatic xenobiotic metabolizing enzymes were studied in male rats. These compounds were administered orally 200 mg/kg/day to the rats for 2 weeks. Both MCPA and clofibrate increased the hepatic level of cytochrome P-450. In the MCPA-treated group, the activities of aniline hydroxylase and 7-ethoxycoumarin O-deethylase increased by 15% and 1.5-fold, respectively. The free acid form of MCPA increased these activities more potently than MCPA. Both MCPA and its free acid did not change the activity of aminopyrine N-demethylase. A marked increase in the activity of aniline hydroxylase was noted in the 2,4-dichlorophenoxyacetic acid-treated group, whereas the aminopyrine N-demethylase activity significantly decreased in the same group. Clofibrate also increased the activities of hepatic microsomal cytochrome P-450-mediated oxidation tested, but to a lesser extent when compared with the effects of MCPA. These results indicate that MCPA may have a potent effect on the hepatic metabolizing enzymes in rats, and also that the induction of xenobiotic metabolizing enzymes may change when the chemical moiety of phenoxyacid compounds is modified.

Effects of ethyl 4-chloro-2-methylphenoxyacetate on hepatic peroxisomal enzymes in rats

Effects of ethyl 4-chloro-2-methylphenoxyacetate (MCPA) and clofibrate on the activities of hepatic lipid metabolizing enzymes in the peroxisomal fraction from rat liver were studied, and these drugs were found to potentiate the peroxisomal enzyme activity. The results imply that MCPA affects lipid metabolism as well as clofibrate.

Differential effects of extra- and intracellular anions on GABA-activated currents in bullfrog sensory neurons

1. Kinetic properties of gamma-aminobutyric acid (GABA)-gated inward and outward anion currents were investigated in the frog sensory neurons perfused internally and externally with various anions with the use of a rapid concentration-jump (termed as 'concentration-clamp') technique. 2. Extracellular Br- [( Br-]o) shifted the dose-response curves of GABA-induced inward anion currents to the left without affecting the maximum values, whereas [Cl-]o, [I-]o, [No3-]o, [HCOO-]o, and [CH3COO-]o altered the rate of desensitization differently without shifting the GABA dose-response curves, indicating that the kinetics of desensitization phase are affected differently by various extracellular anions. 3. [CH3COO-]o suppressed the maximum current of the dose-response curve of the GABA-induced inward ICl without affecting Kd. 4. Both activation and desensitization phases of GABA-induced ICl consisted of fast and slow components, respectively. [Br-]o, [I-]o, and [NO3-]o significantly prolonged the slow desensitization component, whereas both [HCOO-]o and [CH3COO-]o shortened it. The fast desensitization and the fast and slow activation components were also affected by these foreign anions. 5. GABA dose-response curves of inward currents carried by various intracellular anions (Cl-, Br-, NO3-, I-, SCN-, HCOO-, F-, CH3COO-, CH3CH2COO-, BrO3-, and ClO3-) while keeping a constant [Cl-]o had a constant Kd value but different saturating maximum currents. There were no marked differences among their current kinetics except in the case of SCN-, indicating that the current kinetics is not affected by replacing intracellular Cl- [( Cl-]i) with various foreign anions. 6. The configuration and amplitude of GABA-gated outward anion currents at a constant [Cl-]i reflected the extracellular action of individual anions on the anion-binding site of GABA receptor associated with the anion-selective channel. 7. The relative conductances of the various anions, calculated from the maximum peak currents in dose-response curves of the GABA-induced inward anion currents at a constant [Cl-]o, was in the sequence: I- greater than Br- greater than or equal to NO3- greater than ClO3- greater than SCN- greater than or equal to Cl- greater than HCOO- greater than BrO3- greater than CH3COO- greater than F- greater than CH3CH2COO-.(ABSTRACT TRUNCATED AT 400 WORDS)

Activation kinetics of the acetylcholine-gated potassium current in isolated atrial cells

Processes involved in activation of the acetylcholine (ACh) receptor-operated K+ current (IK) were examined in atrial cells isolated from guinea pig using a "concentration-clamp" technique. This approach allows for the intracellular perfusion and the rapid change of external solution (time constant 4 ms) with cell-attached condition under a single-electrode voltage-clamp condition. The ACh-induced IK increased in a sigmoidal fashion with increasing concentrations of ACh. The Ka value estimated from the concentration-response curve was 3 X 10(-7) M, and the Hill coefficient was 1.0. The activation phase was accelerated not only by increasing the concentration of ACh but also by elevating the temperature. Before activation of the current, there was a brief latent period after the application of ACh. The latent period was shortened considerably with the increase in ACh concentration and in temperature, i.e., 267 +/- 20 ms at 18 degrees C, 98 +/- 11 ms at 26 degrees C, and 44 +/- 6 ms at 37 degrees C for 10(-6) M ACh. These results suggest that the latent period of ACh response seems to be the time lag needed for the activation of K+ channels using remote sensor.

Different time courses of the blockade of sodium current by lignocaine and SUN 1165 in single myocytes isolated from guinea-pig atrium

1. The time course of the blockade of sodium currents (INa) by the antiarrhythmic agents, lignocaine and SUN 1165, was studied in single myocytes isolated enzymatically from guinea-pig atrium, by a new concentration-jump termed as a 'concentration-clamp' technique. This technique combines an intracellular perfusion and a rapid exchange of external solution surrounding the voltage-clamped myocyte within 2 ms. 2. Lignocaine (3.7 x 10(-5) M to 3.7 x 10(-4) M) inhibited the peak amplitude of INa in a concentration-dependent fashion. It took 2 to 5s to reach apparent steady-state inhibition at the concentrations used. Complete recovery from the inhibition also took 2 to 5s after washing out the agent. In contrast, the inhibitory effect of SUN 1165 (1 x 10(-5) M) on the peak INa gradually progressed and reached a steady-state level about 2 min after the start of drug-application. The recovery required more than 10 min after washing out of the agent. 3. In cardiomyocytes treated with scorpion toxin (5 micrograms ml-1), the inactivation of INa was greatly inhibited, resulting in the relatively persistent Na inward current (persistent INa) during the depolarizing pulse. Lignocaine (1.1 x 10(-4) M) applied during the depolarizing pulse, reduced in a single-exponential fashion the amplitude of the persistent INa in milliseconds. On the other hand, lignocaine applied several tens of milliseconds before the depolarizing pulse induced only a small reduction of the peak amplitude of the first persistent INa. When SUN 1165 (1 x 10- M) was applied during the depolarizing pulse, there was only a small instantaneous reduction of the amplitude of the persistent I'N, although it did inhibit time-dependently, the peak IN.. Both agents accelerated the decay phase of the persistent IN in a time-dependent manner. 4. These results suggest that lignocaine and SUN 1165 may preferentially interact with the openstate of the sodium channel rather than with the rested one, although SUN 1165 does so much more slowly.

General pharmacological studies on N-(2,6-dimethylphenyl)-8-pyrrolizidineacetamide hydrochloride hemihydrate. 3rd communication: effect on cardiovascular system

In this general pharmacological study of N-[2,6-dimethylphenyl)-8-pyrrolizidineacetamide hydrochloride hemihydrate (SUN 1165), its effects on the cardiovascular and respiratory systems were studied. SUN 1165, at doses of up to 1.0 mg/kg i.v., had almost no effect. SUN 1165, at doses of 3.0 and 6.0 mg/kg i.v., caused dose-dependent decreases in blood pressure, common carotid, vertebral, coronary, hepatic and femoral artery and portal vein blood flows, cardiac contractility, heart rate and myocardial oxygen consumption. SUN 1165 increased urine volume and urinary excretion of electrolytes in rats at a dose of 100 mg/kg p.o. SUN 1165 decreased renal plasma flow and urinary excretion of electrolytes in anesthetized dogs at 6.0 mg/kg i.v., but at the antiarrhythmic doses (1.0-3.0 mg/kg i.v. in dogs), it had almost no effects on renal function. SUN 1165 had almost no effect on the autonomic nervous systems in anesthetized dogs. These results suggest that SUN 1165 at the antiarrhythmic doses do not have any effects on the respiratory and cardiovascular systems, renal function and autonomic nervous systems in rats and dogs, but that when administered at high doses, it has inhibitory effects on respiratory and cardiovascular system and renal function. In conclusion, SUN 1165 seems to be a novel antiarrhythmic drug relatively free of cardiovascular, respiratory, renal and autonomic effects.

Intracellular picrotoxin blocks pentobarbital-gated Cl- conductance

Using the 'inside-out' configuration of frog sensory neurons, we studied the effect of intracellular picrotoxin on the pentobarbital-gated single channel response of Cl- -current (iCl). The pentobarbital-induced iCl showed no voltage-dependency and the single channel conductance (gamma Cl) was 16 +/- 3.1 pS (n = 6). Picrotoxin caused the pentobarbital-gated Cl- channels to react in a flickering pattern and then finally caused them to cease their opening altogether. This inhibitory action of picrotoxin was reversible.

Effects of diuretics on GABA-gated chloride current in frog isolated sensory neurones

1. Effects of three diuretics (furosemide, amiloride and alpha-human atrial natriuretic polypeptide (alpha-hANP] on GABA-activated chloride current (ICl) were investigated in frog isolated sensory neurones, following suppression of Na+, K+ and Ca2+ currents, by use of a 'concentration-clamp' technique. 2. Furosemide inhibited the GABA-activated ICl in a non-competitive manner and facilitated the inactivation phase, while amiloride inhibited the GABA response in a competitive manner, both inhibitions being concentration-dependent. Alpha-hANP had no effects on the GABA-induced ICl. 3. The reversal potential of GABA-activated ICl (EGABA) was not shifted in the presence of amiloride or furosemide. 4. The results suggest that amiloride may act at the GABA binding site while furosemide may act on the GABA-gated chloride channel.

Mechanism of inhibition by SUN 1165, a new Na channel blocking antiarrhythmic agent, of cardiac glycoside-induced triggered activity

The mechanism of the antiarrhythmic action of SUN 1165, a selective Na channel blocker, in digitalis-induced arrhythmias was investigated by means of conventional microelectrode and suction pipette methods with isolated canine Purkinje fibers and guinea-pig single ventricular cells, respectively. SUN 1165 decreased acetylstrophanthidin-induced delayed afterdepolarization and completely blocked the initiation of triggered activity by acetylstrophanthidin in Purkinje fibers. Delayed afterdepolarization, which was completely abolished either by intracellular dialysis with EGTA or by extracellular superfusion with caffeine, was decreased by SUN 1165 in a concentration-dependent manner in single ventricular cells. These results suggest that an increase in intracellular Ca2+ concentration is a requirement for delayed afterdepolarization. Furthermore, the antiarrhythmic action of SUN 1165 in cardiac glycoside-induced arrhythmias in dogs could be mediated not only by an inhibition of sodium channels and subsequent reduction in the intracellular sodium activity, but also by a reduction of intracellular calcium activity due to the Na+-Ca2+ exchange mechanism.

Protective effect of alpha-human atrial natriuretic polypeptide (alpha-hANP) on chemical-induced pulmonary edema

It has been established that alpha-hANP, the newly discovered peptide extracted from human cardiac atria, has potent natriuretic and hypotensive actions. Our present investigation is the first to demonstrate that alpha-hANP is capable of protecting against pulmonary edema caused by various chemicals, using isolated perfused guinea pig lung system. Lungs were perfused via pulmonary artery with Krebs-Ringer bicarbonate buffer at 5.0 ml/min, and wet weight of lungs and perfusion pressure of pulmonary artery (Pa) were monitored. Bolus injection of Triton-X or CHAPS into cannulated pulmonary artery produced edema as indicated by a massive increase in wet weight and a slight increase in Pa. Constant infusion of alpha-hANP through pulmonary artery at 200 ng/ml was effective in causing decrease in wet weight of lung. Perfusion of lung with paraquat or PGF2 alpha, and repeated bolus injection of arachidonic acid or PGE2 caused elevation in both wet weight of lung and Pa. The treatment with alpha-hANP similar to that described above also protected against edema caused by paraquat or arachidonic acid. Bolus administration of epinephrine induced a slight increase in wet weight and Pa, and alpha-hANP was effective in decreasing the elevated lung wet weight and Pa of lungs. Infusion or bolus administration of alpha-hANP into control lungs increased cGMP level in outflow perfusate as well as in lung tissue significantly. In lungs with edema which were induced by Triton-X or paraquat, there was a slight increase in cGMP level in Triton-X treated and no increase in paraquat treated lung tissues. In either cases, was there any increase in cGMP level in perfusate. The specific binding study of [125I]alpha-hANP revealed that the lack of increase in cGMP was not due to a loss of receptor in Triton-X or paraquat treated lungs. Thus our study demonstrated that alpha-hANP had a direct anti-edematic action(s) in lung which was not secondary to the systemic natriuretic and/or hypotensive action(s).

Contribution of chloride shifts to the fade of gamma-aminobutyric acid-gated currents in frog dorsal root ganglion cells

1. The contribution of Cl- redistribution to the decay phase of the GABA (gamma-aminobutyric acid) response was investigated in isolated frog sensory neurones, using a suction-pipette technique which allows for internal perfusion under conditions of voltage clamp. 2. In neurones perfused with 120 mM [Cl-]i and [Cl-]o at driving forces (delta VH) of less than 15 mV, no shift of GABA equilibrium potential (EGABA) occurred during a continuous application of GABA, at various concentrations. However, increases of delta VH towards negative or positive potentials over 15 mV induced EGABA shifts. 3. The degree of EGABA shift was governed by the total amount of Cl- flux across the soma membrane, an event which depends upon delta VH, GABA concentration and drug application time. 4. The time-dependent EGABA shift due to Cl- redistribution during GABA application induced a current run-down resulting from a decreased Cl- gradient and a diminished Cl- conductance (gCl), the latter brought about by a drop in the intracellular ionic density of Cl-. 5. The EGABA shift during a continuous GABA application was also affected by [Cl-]i; e.g. the shift more readily occurred at lower [Cl-]i. 6. In neurones perfused with internal and external solutions containing 120 mM-Cl- at a delta VH of less than 10 mV, the change of gCl occurred with no shift of EGABA during the continuous application of GABA at concentrations over 6 x 10(-5) M, thereby indicating a 'real' GABA receptor desensitization. The desensitization depended solely upon the agonist concentrations but not upon the amount of ICl. Under these conditions, the time course of recovery from GABA desensitization was estimated. The decrease of gCl at the desensitization phase was a single exponential. 7. At a delta VH greater than 15 mV, therefore, the decay of ICl induced by GABA concentrations over 6 x 10(-6) M consists of the sum of both the 'real' GABA receptor desensitization and the current run-down brought about by Cl- shifts. The gCl at the current decay phase consisted of a double exponential. In the present experiments we chose experimental conditions with which Cl- shift become negligible. 8. The 'pure' GABA receptor desensitization during a continuous application of GABA developed rapidly at GABA concentrations over 10(-5) M. The speed of desensitization was facilitated by increasing the magnitude of desensitization.