Acute or chronic exercise alters angiotensin II-induced contraction of rat aorta

Chronic exercise substantially shifted the dose-response curve for angiotensin II (ANG II)-induced contractions to the right with increases in the EC50 value in both endothelium-intact and endothelium-denuded aortae. An acute endurance exercise also caused a 3-fold increase in the EC50 value in both endothelium-intact and endothelium-denuded aortae from sedentary control rats. Whereas, no substantial increase in the EC50 value was observed in trained rats after an acute endurance exercise. Thus, chronic exercise attenuates ANG II receptor-mediated contraction of rat aortae. An acute exercise also caused the reduced responses to ANG II in sedentary control rats but not in chronically exercise-trained rats.

Ca2+ and lipolysis in adipocytes from exercise-trained rats

The effects of Ca2+ on lipolysis and protein kinase activity in adipocytes from exercise-trained rats were investigated. Chronic exercise significantly increased lipolytic responses to norepinephrine and dibutyryl adenosine 3',5'-cyclic monophosphate (cAMP). The inhibitory effects of N-(6-aminohexyl)-5-chloro-1-naphthalene sulfonamide (W-7), a calumodulin inhibitor, on norepinephrine- and dibutyryl cAMP-stimulated lipolysis were significantly greater in trained than in sedentary rats. Training did not alter cAMP-dependent protein kinase activity. However, the inhibitory effect of W-7 on cAMP-dependent protein kinase activity was much greater in trained than in sedentary rats. The basal intracellular free Ca2+ concentration ([Ca2+]i) was significantly higher in trained than in sedentary rats. The rapid and transient increases in [Ca2+]i due to adrenocorticotropic hormone and phenylephrine from basal levels were significantly lower in trained than in sedentary rats. However, the higher basal [Ca2+]i level in trained rats led to increases in sustained [Ca2+]i levels after stimulation. We concluded that in trained rats the regulation of protein kinase activity by cAMP depends to a greater degree on Ca(2+)-calmodulin complex than it does in sedentary rats and that training alters adipocyte intracellular Ca2+ homeostasis, including [Ca2+]i responsiveness to hormones.

Cyanoamidines. II. Synthesis and pharmacological activity of N-arylalkyl-N'-cyano-3-pyridinecarboxamidines

A new series of cyanoamidines, N-arylalkyl-N'-cyano-3-pyridinecarboxamidines was synthesized and evaluated for inhibitory effects on 40 mM KCl-induced contraction and norepinephrine (NE)-induced contraction of rat aorta strips. The N-phenethyl cyanoamidine 4c showed potent vasodilatory action. Further in vitro screening program using 4c as a lead compound resulted in the discovery of highly potent N-[2-(2-chlorophenyl)ethyl]-N'-cyano-3-pyridinecarboxamidine (5j). Compound 5j induced the greatest increase in 86Rb+ efflux among cyanoamidine series. Subsequent modification of the pyridine ring of 5j was performed with evaluation for intravenous and oral antihypertensive activities. Introduction of an amino group at the 5-position of the pyridine ring furnished the new potassium channel opener, 5-amino-N-[2-(2-chlorophenyl)ethyl]-N'-cyano-3-pyridinecarboxamidine+ ++ (9e; KRN4884), which showed highly potent antihypertensive activity and a long duration of antihypertensive action after oral administration. KRN4884 is under further development as an antihypertensive agent.

Comparative vasodepressor effects of 3-pyridine derivatives possessing the cyanoamidine or amide structure in pithed rats

The potency and mechanism of the vasodepressor action of N-cyano-3-pyridinecarboximidamide and nicotinamide, which are 3-pyridine derivatives possessing cyanoamidine and amide structures, respectively, were studied in pithed rats infused with phenylephrine. The N-substituents of cyanoamidine and amide in the derivatives studied comprised 2-nitroxyethyl (KRN2391 and nicorandil), phenethyl (Ki769 and Ki765) and 2-(2-chlorophenyl)ethyl (Ki3005 and Ki4261) moieties. These derivatives produced vasodepressor actions in a dose-dependent manner, except for Ki4261 which did not show any action below the solubility limit. When the vasodepressor effects of compounds possessing the same N-substituents in cyanoamidine and amide derivatives were compared, the potency of cyanoamidine derivatives was greater than that of amide derivatives, Ki3005 being the most potent. The vasodepressor effects of cyanoamidine and amide derivatives were antagonized by glibenclamide, although the antagonism of the depressor effects of KRN2391 and nicorandil was less pronounced than that of the other derivatives. These results suggest that N-substituents, in addition to the cyanoamidine structure, play an important role in determining the vasodepressor potencies of 3-pyridine derivatives. Furthermore, the vasodepressor effects of these derivatives appear to be based on their K+ channel-opening actions, although those of KRN2391 and nicorandil seem to be partly mediated by a nitrate-like action in addition to their K+ channel-opening action.

Vasospasmolytic effect of KRN2391 on 3,4-diaminopyridine-induced rhythmic contraction of porcine coronary artery

1. In the present study, we examined the vasospasmolytic effect of KRN2391 on rhythmic contractions of porcine coronary artery caused by 3,4-diaminopyridine (3,4-DAP) compared with cromakalim and nitroglycerin. 2. KRN2391 at 10(-7) showed a tendency to prolong the cycle length and at 10(-6) M completely eliminated rhythmic contractions in all preparations. The elimination by 10(-6) M KRN2391 was antagonized by either oxyhemoglobin (10(-5) M) or glibenclamide (3 x 10(-6)) although not completely. 3. Cromakalim at 10(-5) M and nitroglycerin at 10(-7) M completely eliminated 3,4-DAP-induced rythmic contractions in all preparations. The elimination by cromakalim and nitroglycerin was completely antagonized by glibenclamide and oxyhemoglobin, respectively. 4. The present study suggests that the vasospasmolytic effect of KRN2391 on 3,4-DAP-induced rhythmic contractions is based on its nitrate action and K channel opening action.

Pharmacological analysis of the inhibitory effects of KRN2391 on endothelin-1-induced contraction in isolated large coronary artery of the pig

1. The relaxant effect of KRN2391, N-cyano-N'-(2-nitroxyethyl)-3-pyridine-carboximidamide-mo nomethanesulfonate (with both K+ channel opener and nitrate actions), nifedipine (Ca2+ channel blocker), nitroglycerin (nitrate) and cromakalim (K+ channel opener) were investigated in isolated porcine large coronary arteries contracted by endothelin-1. These drugs inhibited endothelin-1-induced contraction in a concentration-dependent manner. 2. The relaxation induced by KRN2391 was nearly complete at their maximum effects, but nifedipine and cromakalim could not produce complete relaxation. 3. The concentration-relaxation curves for KRN2391 underwent a rightward shift in the presence of methylene blue or glibenclamide. The concentration ratios of KRN2391 calculated based on EC50 values were 2.8 and 3.7 in the presence of methylene blue and glibenclamide, respectively. 4. The concentration-relaxation curves for nitroglycerin and cromakalin underwent a rightward shift in the presence of methylene blue and glibenclamide, respectively, and the concentration ratios of nitroglycerin and cromakalim were 12.0 and 6.3. 5. These relaxant effects of KRN2391 and nitroglycerin on endothelin-1-induced contraction of porcine coronary artery were greater than those of cromakalim and nifedipine. This potent relaxant action of KRN2391 on endothelin-induced contraction is thought to be based on both a nitrate action and a K+ channel opening action.

Cardiovascular effects of KRN2391, nitroglycerin and cromakalim in dihydroergotamine-treated pithed rats

1. The effects of KRN2391 on the cardiovascular system were compared with those of nitroglycerin and cromakalim in pithed rats treated with dihydroergotamine (DHE) in order to examine the effects of these drugs on venous blood vessels. 2. DHE (100 micrograms/kg, i.v.) produced increases in mean blood pressure (MBP), cardiac output (CO) and central venous pressure (CVP) without changes in total peripheral vascular resistance (TPR) and heart rate (HR) based on venoconstriction. The DHE-treated pithed rats, nitroglycerin (30 micrograms/kg, i.v.) decreased CO and CVP whereas cromakalim (30 micrograms/kg, i.v.) produced a slight increase in CO followed by a decrease and did not affect CVP. KRN2391 (30 micrograms/kg, i.v.) produced a decrease in CVP without affecting CO. Decreases in MBP and TPR were induced by all drugs. 3. These results suggest that nitroglycerin acts predominantly as a venodilator and KRN2391 and cromakalim showed a venodilating action in addition to an arterial dilating action in DHE treated pithed rats. However, the venodilating action of KRN2391 in this condition is more potent than that of cromakalim.

The rice bZIP transcriptional activator RITA-1 is highly expressed during seed development

Systematic protein-DNA binding studies have shown that plant basic leucine zipper (bZIP) proteins exhibit a differential binding specificity for ACGT motifs. Here, we show that the rice transcription activator-1 (RITA-1) displays a broad binding specificity for palindromic ACGT elements, being able to bind A-, C-, and G-box but not T-box elements. By using gel mobility shift assays with probes differing in sequences flanking the hexameric core, we identified high-affinity A-, C-, and G-box binding sites. Quantitative and competition DNA binding studies confirmed RITA-1 specificity for these sites. Using rice protoplasts as a transient expression system, we demonstrated that RITA-1 can transactivate reporter genes possessing high-affinity but not low-affinity RITA-1 binding sites. Our results established a direct relationship between in vivo transactivation and in vitro binding activity. Transient expression assays that demonstrated the ability of RITA-1 to transactivate a construct containing rita-1 5' flanking sequences suggest that the factor may be autoregulated. Histochemical analysis of transgenic rice plants showed that a rita-1-beta-glucuronidase transgene is expressed in aleurone and endosperm cells of developing rice seeds. We propose that RITA-1 plays a role in the regulation of rice genes expressed in developing rice seeds.

Comparative analysis of vasodilating mechanisms of Ki1769, Ki3315 and KRN2391, pyridinecarboximidamide derivatives, in porcine isolated coronary artery

1. The vasodilating mechanisms of pyridinecarboximidamide derivatives which have a nitroxyl group (KRN2391), a phenyl group (Ki1769) or a hydroxyl group (Ki3315) were studied in porcine isolated coronary artery. 2. KRN2391 (10(-6) M) increased cyclic GMP formation but did not affect intracellular cyclic AMP level. Ki1769 (10(-5) M) and Ki3315 (10(-3) M) had no effect on intracellular cyclic GMP and cyclic AMP levels. 3. Despite producing submaximal relaxation at KRN2391 (10(-6) M) and nitroglycerin (10(-6) M), the increase in cyclic GMP caused by KRN2391 was lower than that caused by nitroglycerin. 4. Methylene blue (10(-5) M) inhibited KRN2391- and nitroglycerin-induced relaxations but did not affect Ki1769- and Ki3315-induced relaxation. 5. Glibenclamide (10(-6) M) inhibited KRN2391-, Ki1769- and Ki3315-induced relaxation but did not affect nitroglycerin-induced relaxation. 6. These results suggest that the nitroxyl group of KRN239 contributes to its nitrate action and the pyridinecarboximidamide moiety plays an important role of developing a K channel opening action.

Pharmacological analysis of the effect of KRN2391 on coronary vasculature in perfused rat heart

1. The antagonism by glibenclamide of the effects of KRN2391, cromakalim and nifedipine on coronary flow (CF) were compared in isolated perfused rat hearts. 2. KRN2391, cromakalim and nifedipine increased CF in a concentration-dependent manner. In the presence of glibenclamide, the concentration-effect curves on CF for KRN2391 and cromakalim shifted to the right but that for nifedipine did not change. 3. The EC50 values increased about 6.6-fold for KRN2391 and 19.0-fold for cromakalim in the presence of glibenclamide. 4. These results suggest that the increase in CF induced by KRN2391 is due to both glibenclamide-sensitive and insensitive mechanisms.

[A case of motor and sensory neuropathy associated with metatropic dysplasia]

We reported a case of a fifteen-year-old boy with metatropic dysplasia. He showed short-limbed dwarfism at the age of 1 year and 2 months. Roentgenograms of the bone revealed generalized platyspondyly, enlargement of the epiphyseal-metaphyseal regions of long bones and halberd-shaped pelvis. Scoliosis progressed and he evolved to short-trunk dwarfism. When he was 10 years old, he developed gait disturbance gradually due to muscle weakness of lower extremities. He was examined at the age of 15 years. Motor nerve conduction velocity was reduced to 21 m/sec in left median nerve and 18.5 m/sec in left peroneus nerve. Needle EMG showed neurogenic pattern. We performed sural nerve biopsy and obtained histopathological findings. Fiber density of myelinated axons decreased. Electron microscopic examination revealed onion bulb formation surrounding a myelinated fiber and a storage in the rough-surfaced endoplasmic reticulum of Schwann cell. These inclusions were similar to those of cartilage of his long bone. We supposed that the neuropathy would have relation to this bone dysplasia.

Increase in cytosolic free Ca2+ in corticotropin-stimulated white adipocytes

The mechanism of the adrenal corticotropin hormone (ACTH)-stimulated increase in cytosolic free Ca2+ concentration ([Ca2+]i) was investigated in rat white adipocytes. ACTH at concentrations > 10 mU/ml caused a rapid and transient increase in [Ca2+]i followed by a small but sustained elevation of [Ca2+]i. A similar phenomenon was also induced by alpha-adrenergic or synthetic ACTH stimulation. The effect of norepinephrine (NE) plus ACTH on [Ca2+]i was nearly additive. Pertussis toxin completely blocked the ability of ACTH or NE to increase [Ca2+]i. NE but not ACTH caused a significant increase in inositol 1,4,5-trisphosphate levels. ACTH caused a rapid and transient accumulation of [3H]arachidonic acid (AA) and a marked loss of [3H]AA from phosphatidylinositol (PI) and phosphatidylcholine (PC) 10 s after stimulation. Neither a lipoxygenase inhibitor nor a dual inhibitor of cyclooxygenase and lipoxygenase blocked the increases in [Ca2+]i and the accumulation of [3H]AA in response to ACTH. On the other hand, either pertussis toxin or phospholipase A2 inhibitor drastically blocked both parameters in response to ACTH. These results indicate that ACTH stimulates AA release from PC and PI via the activation of phospholipase A2 coupled with pertussis toxin-sensitive GTP-binding protein(s), which leads to an increase in [Ca2+]i in rat white adipocytes.

Characteristics of Ki1769, a novel vasodilator, in isolated rat aorta

The vasorelaxant mechanism of a newly synthesized vasodilator, Ki1769 [N-cyano-N'-(2-phenethyl)-3-pyridinecarboximidamide], was studied in isolated rat aorta in comparison with cromakalim. Ki1769 (10(-8)-10(-5) M) and cromakalim (10(-8)-10(-5) M) produced a concentration-dependent relaxation and the EC50 values for Ki1769 and cromakalim were (8.60 +/- 1.90) x 10(-7) M and (1.36 +/- 0.18) x 10(-7) M, respectively. Ki1769- and cromakalim-induced relaxations were competitively antagonized by glibenclamide with pA2 values of 6.83 and 6.93, respectively. Charybdotoxin, apamine, atropine, propranolol and indomethacin did not affect the Ki1769-induced relaxation. An increase in 86Rb efflux was induced by Ki1769. Glibenclamide attenuated the increase in 86Rb efflux produced by Ki1769. These results suggest that the vasorelaxant effect of Ki1769 is based on the glibenclamide-sensitive K channel-opening action.

Cardiovascular effects of KRN2391 in anesthetized dogs: a comparison with cromakalim and nitroglycerin

The cardiovascular effects of KRN2391, N-cyano-N'-(2-nitroxyethyl)-3-pyridine carboximidamide monomethanesulfonate, were compared with those of cromakalim and nitroglycerin in anesthetized dogs. KRN2391 (3-30 micrograms/kg, i.v.), cromakalim (3-30 micrograms/kg, i.v.) and nitroglycerin (1-10 micrograms/kg, i.v.) produced a dose-related decrease of the mean blood pressure with concomitant increase in heart rate. The increase in heart rate caused by cromakalim was lower than that caused by KRN2391 and nitroglycerin. Left ventricular end-diastolic pressure was decreased by all doses of KRN2391 and nitroglycerin. Cromakalim at 3 and 10 micrograms/kg decreased this end-diastolic pressure but increased it at 30 micrograms/kg. Left ventricular dP/dt was increased by KRN2391 and nitroglycerin but was decreased by cromakalim. KRN2391 and cromakalim produced a dose-dependent increase in aortic and coronary blood flow. Nitroglycerin showed biphasic changes in aortic and coronary blood flow, i.e., an initial increase followed by a decrease. At equipotent hypotensive doses, the increase in coronary blood flow induced by KRN2391 was greater than that by cromakalim and nitroglycerin, and total peripheral and coronary vascular resistances were decreased by KRN2391 and cromakalim. Nitroglycerin showed biphasic changes in total peripheral and coronary vascular resistances, i.e., these resistance showed an initial decrease followed by an increase. The relative decrease of coronary vascular resistance compared to the total peripheral vascular resistance was greater for KRN2391 than for cromakalim and nitroglycerin. The changes in hemodynamic parameters caused by KRN2391 were inhibited by pretreatment with glibenclamide (5 mg/kg, i.v.). These results suggest that the hemodynamic profile of KRN2391 is closer to that of cromakalim than to that of nitroglycerin, but that the selectivity for the coronary vascular bed is higher for KRN2391 than for cromakalim. In addition, it is considered that, compared with KRN2391 and nitroglycerin, cromakalim has a low selectivity for the vasculature vs the myocardium.

Comparison of coronary dilating effects of Ki1769, a new K channel opener of the pyridinecarboximidamide type, and nifedipine in anesthetized dogs

The coronary dilating effect of a new type of K channel opener, N-cyano-N'-(2-phenethyl)-3-pyridinecarboximidamide (Ki1769), was examined in anesthetized dogs in comparison with that of nifedipine. Administration of Ki1769 (30 and 100 micrograms/kg, i.v.) and nifedipine (1 and 3 micrograms/kg, i.v.) produced a dose-dependent decrease of mean blood pressure with a concomitant increase in heart rate. Ki1769 and nifedipine dose-dependently increased coronary blood flow and aortic blood flow and decreased coronary vascular resistance and total peripheral vascular resistance. The percentage decrease of coronary vascular resistance was greater than that of total peripheral vascular resistance with Ki1769 and nifedipine, but Ki1769 showed a greater specificity in the decrease of coronary vascular resistance than nifedipine. Glibenclamide (5 mg/kg, i.v.) inhibited these hemodynamic effects of Ki1769 but did not affect those of nifedipine. These results suggest that the preferential effect of Ki1769 on the coronary vascular bed is greater than that of nifedipine. Such a profile of Ki1769 is based on its K channel-opening action.

Plant bZIP proteins gather at ACGT elements

ACGT cis-acting DNA sequence elements have been identified in a multitude of plant genes regulated by diverse environmental, physiological, and environmental cues. In vivo transient and transgenic plant expression studies have shown that these ACGT elements are necessary for maximal transcriptional activation. Plants possess a conserved family of DNA-binding proteins specific for these DNA sequence motifs. Well-defined in terms of nucleotide sequence required for protein/DNA interactions and transcriptional activation, various ACGT elements have been used as molecular probes to clone sequence-specific DNA binding proteins. All plant DNA-binding proteins specific for ACGT elements belong to the bZIP classification. Most recombinant bZIP proteins can interact with ACGT elements derived from different plant genes, albeit with different affinity. Systematic protein/DNA binding studies have shown that sequences flanking the ACGT core affect bZIP protein binding specificity. These studies have provided the basis for a concise ACGT nomenclature and defined high-affinity A-box, C-box, and G-box elements. Plant bZIP factors can be classified according to their quantitative binding affinities for high-affinity ACGT elements. Potential molecular mechanisms that may control how plant bZIP proteins activate plant gene expression are discussed.

Differential vasodilator properties of KRN2391, cromakalim, nitroglycerin and nifedipine in rabbit isolated femoral artery and vein

1. The selectivity for artery and vein of KRN2391, cromakalim, nitroglycerin and nifedipine was examined in isolated femoral artery and vein preparations of the rabbit. 2. All drugs produced a concentration-dependent relaxation in both femoral artery and vein. 3. Nitroglycerin was more potent in femoral vein than in femoral artery at all concentrations. The EC50 value obtained in the vein was about 14 times smaller than that obtained in artery. 4. Cromakalim and nifedipine were almost equipotent on both vascular preparations. Cromakalim at the highest concentration (10(-5) M) produced 88 and 78% relaxation in femoral artery and vein, respectively. The maximum relaxation induced by nifedipine (10(-6) M) was less than 50% in both preparations. 5. KRN2391 was active at a lower concentration in the vein than in the artery and its maximum relaxation at 10(-5) M was about 90% in both preparations. 6. Glibenclamide (10(-6) M) inhibited the vasorelaxation caused by KRN2391 in both artery and vein. Methylene blue (10(-5) M) also inhibited the relaxant action of KRN2391 but this action was slight in the artery. 7. These results suggest that KRN2391 and nitroglycerin are more potent in the vein than in the artery and cromakalim and nifedipine are equipotent in both. It is considered that the relaxation induced by low concentrations of KRN2391 reflects predominantly its action as a nitrate and that at high concentrations it acts as a K+ channel opener in addition to its nitrate action. The different vascular selectivities of these drugs are thought to relate to the differences in their mechanisms of action in vascular smooth muscle.

Lack of the stimulatory effect of guanine nucleotide on diacylglycerol generation in permeabilized adipocytes from diabetic rats

Insulin caused an 8- or a 3-fold increase in lipogenesis in control rats (C) or diabetic rats (DM), respectively. Following insulin treatment for DM, insulin resistance was clearly reversed. Phospholipase C (PLC) caused a 4-fold increase in lipogenesis in C, but not in DM. Insulin treatment partially restored PLC-induced lipogenesis. Insulin or PLC increased protein kinase C (PKC) activity in the membrane fraction in C, but not in DM. Insulin treatment partially restored insulin- or PLC-stimulated PKC activity. 5'-Guanylylimidodiphosphate (Gpp(NH)p) exerted a stimulatory effect on diacylglycerol (DAG) generation in permeabilized adipocytes from C, but not in DM. Insulin treatment partially restored the stimulatory effect of Gpp(NH)p. These findings suggest that a particular G protein(s) is involved in the regulation of DAG generation in adipocytes, and that diabetes leads to a functional or quantitative abnormality in G protein and G protein-PLC. Insulin therapy partially restored G protein-PLC dependent glucose uptake.

In vitro and in vivo K channel-opening effects of Ki3315, a metabolite of the novel vasodilator KRN2391

The vasodilating potencies and mechanism of action of KRN2391 [N-cyano-N'-(2-nitroxyethyl)-3-pyridinecarboximidamide monomethanesulfonate] and its metabolite Ki3315 [N-cyano-N'-(2-hydroxyethyl)-3-pyridinecarboximidamide] were investigated in rat isolated aortae and in pithed rats. In experiments using rat isolated aortae, Ki3315 (10(-5)-3 x 10(-4) M) and KRN2391 (10(-8)-10(-4) M) produced concentration-dependent relaxations. However, the vasodilating potency of Ki3315 was about 1000-fold lower than that of KRN2391. The relaxant effect of KRN2391 was antagonized by both methylene blue and glibenclamide, whereas that of Ki3315 was only antagonized by glibenclamide. In experiments using pithed rats, cumulative administration of Ki3315 (0.3-30 mg/kg, i.v.) and KRN2391 (3-300 micrograms/kg, i.v.) produced a dose-dependent decrease of diastolic blood pressure. The vasodepressor effect of Ki3315 was weaker than that of KRN2391. In rats given glibenclamide (20 mg/kg, i.v.), the vasodepressor curves for Ki3315 and KRN2391 were shifted to the right. The ED50mmHg values increased about 5-fold for KRN2391 and 8.2-fold for Ki3315 in glibenclamide-treated rats. These results suggest that Ki3315 and KRN2391 show vasorelaxant effects in vitro and in vivo, but in this respect Ki3315 is weaker than KRN2391. These effects of Ki3315 are predominantly due to a K channel-opening action, while those of KRN2391 involve a nitrate action in addition to a K channel-opening action.

Pharmacological analysis of the vasodepressor effect of KRN2391 in pithed rats

1. The antagonism by glibenclamide of the vasodepressor effects of KRN2391, cromakalim and nitroglycerin was compared in pithed rats with blood pressure supported by an infusion of phenylephrine. 2. Cumulative administration of KRN2391 (3-300 micrograms/kg, i.v.), cromakalim (3-300 micrograms/kg, i.v.) and nitroglycerin (1-300 micrograms/kg, i.v.) produced dose-dependent decreases in diastolic blood pressure. 3. In rats given glibenclamide (20 mg/kg, i.v.) the dose-vasodepressor curves for KRN2391 and cromakalim were shifted to the right. However, glibenclamide had no effect on the vasodepressor effect of nitroglycerin. 4. The ED50mmHg values increased about 5.9 fold for KRN2391 and 9.5 fold for cromakalim in glibenclamide-treated rats. 5. These results suggest that the vasodepressor effect of KRN2391 is due to both glibenclamide-sensitive and insensitive mechanisms. This glibenclamide-insensitive effect of KRN2391 is thought to reflect its nitrate action.

Vasorelaxant action of Ki1769, a new pyridinecarboximidamide, in isolated porcine coronary artery

The characteristics of KRN2391 (N-cyano-N'-(2-nitroxyethyl)-3-pyridinecarboximidamide monomethansulfonate) and its phenethyl and 2-hydroxyethyl derivatives (Ki1769 and Ki3315) were studied in isolated porcine coronary arteries. KRN2391, Ki1769 and Ki3315 produced concentration-dependent relaxation of coronary arteries contracted by 25 mM KCl and the order of relaxant potency was KRN2391 > Ki1769 > Ki3315. At the maximum effect, KRN2391 produced nearly complete relaxation but Ki1769 produced about 66% relaxation. The maximum effect of Ki3315 could not be obtained because of its solubility. The relaxation induced by KRN2391 was antagonized by glibenclamide and methylene blue but relaxations caused by Ki1769 and Ki3315 were antagonized by glibenclamide alone. The antagonistic effect of glibenclamide on Ki1769- and Ki3315-induced relaxations was more potent than that on KRN2391-induced relaxation. KRN2391 induced relaxation of coronary arteries contracted by 40 mM KCl in a concentration-dependent manner but the effect of KRN2391 was smaller against 40 mM KCl-induced contractions than against 25 mM KCl-induced contractions. Ki1769 had almost no effect on coronary arteries contracted by 40 mM KCl. These results suggest that pyridinecarboximidamide derivatives which do not possess a nitroxyl group have vasodilating ability based on a K+ channel opening action.

Mechanism of isoprenaline-stimulated diacylglycerol formation in rat parotid acinar cells

The kinetics and mechanism of sn-1,2-diacylglycerol (DAG) formation induced by isoprenaline were studied in rat parotid acinar cells. DAG accumulation induced by 100 microM isoprenaline reached its maximum at 1 min, rapidly decreased (about 50%) at 5 min and then remained constant for 30 min. DAG accumulation 1 min after isoprenaline treatment was dose-dependent. Either propranolol or phentolamine inhibited isoprenaline-stimulated DAG accumulation in a dose-dependent manner. Addition of a vasoactive intestinal polypeptide, forskolin, or dibutyryl cyclic AMP had no effect on DAG accumulation. Isoprenaline did not cause the release of [3H]choline or [3H]ethanolamine metabolites into the medium. Based on the kinetics of DAG formation and [32P]phosphoinositide breakdown, we conclude that isoprenaline-induced DAG formation was mainly related to the hydrolysis of [32P]phosphatidylinositol 4,5-bisphosphate ([32P]PIP2). These results suggest that the effect of isoprenaline on DAG formation is mediated by alpha 1-adrenoceptor activation, that it is not related to the increase in cyclic AMP, and that it is closely related to PIP2 hydrolysis.

Effects of KRN2391, nicorandil and diltiazem on the changes in the electrocardiogram caused by endothelin-1 in anaesthetized rats

1. The effect of KRN2391, a novel vasodilator, on the changes of electrocardiogram caused by endothelin-1 (ET-1) was studied in anaesthetized rats and compared with the effects of nicorandil and diltiazem. In addition, the effect of KRN2391 on the action potential of guinea-pig papillary muscle was studied. 2. The intracoronary administration (i.c.) of ET-1 (5 micrograms) induced not only ST segment elevation of the electrocardiogram due to contraction of the coronary artery, but also arrhythmias involving atrioventricular block (A-V block), ventricular premature contraction (VPC) and ventricular fibrillation (VF), and resulted in death in most animals. However, the administration of methacholine (3 micrograms, i.c.) produced ST segment elevation alone without developing arrhythmias. 3. Pretreatment with intravenous administration of KRN2391 (30 micrograms kg-1) inhibited the ST segment elevation and the development of arrhythmias induced by ET-1, and decreased the incidence of death. 4. Nicorandil (1000 micrograms kg-1) prevented the ST segment elevation without suppression of the occurrence of VF. Diltiazem (100 micrograms kg-1) suppressed both the ST segment elevation and the occurrence of VF but not other arrhythmias. Nicorandil at 3000 micrograms kg-1 and diltiazem at 300 micrograms kg-1 produced not only a suppression of ST segment elevation and VF incidence but also a decrease in the occurrence of arrhythmias. These doses of nicorandil and diltiazem produced a decrease in death in a dose-dependent manner. 5. KRN2391 (10 and 30 micrograms kg-1), nicorandil (1000 and 3000 micrograms kg-1) and diltiazem (100 and 300 micrograms kg-1) significantly decreased mean blood pressure in a dose-dependent manner. Heart rate was decreased by nicorandil (3000 microg kg-1) and diltiazem (100 and 300 microg kg-1) but was not affected byKRN2391 (10 and 30 microg kg-1).6. KRN2391 (30 microM) significantly shortened the action potential duration of guinea-pig ventricle at 50% and 90% repolarization (APD50 and APD90). The effect of KRN2391 was inhibited by a K+channel blocker, glibenclamide (30 microM).7. These results suggest that the occurrence of ST segment elevation and arrhythmias induced by ET-1 are due to a dual direct action on both coronary vascular smooth muscle and myocardium. Therefore,the protective effects of KRN2391, nicorandil and diltiazem on ET-l-induced heart disorders appear to be due to their direct actions on coronary vascular smooth muscle and the myocardium.

In vivo adaptative regulation of muscarinic receptors and muscarinic stimulation-induced Ca2+ mobilization during short-term heat exposure in rat parotid glands

1. Adaptation of muscarinic receptors (MR)--muscarinic stimulation--induced intracellular Ca2+ mobilization during short-heat exposure (33 degrees C). 2. Heat-exposure for 48 hr decreased the carbachol (CCh)-stimulated cytosolic Ca2+ concentration increase. 3. The number of MR on cell surface increased transiently at 24 hr with a subsequent decrease at 48 hr. 4. CCh-stimulated inositol triphosphate (IP3) formation decreased at 48 hr. 5. In saponin-permeabilized cells, 1,4,5-IP3-induced 45Ca2+ release decreased at 24 hr. 6. The data suggest that the adaptation for increased muscarinic stimulation occurs at IP3 generating sites as well as at intracellular IP3 receptor sites during heat exposure.

Trans-activation and stable integration of the maize transposable element Ds cotransfected with the Ac transposase gene in transgenic rice plants

To develop an efficient gene tagging system in rice, a plasmid was constructed carrying a non-autonomous maize Ds element in the untranslated leader sequence of a hygromycin B resistance gene fused with the 35S promoter of cauliflower mosaic virus. This plasmid was cotransfected by electroporation into rice protoplasts together with a plasmid containing the maize Ac transposase gene transcribed from the 35S promoter. Five lines of evidence obtained from the analyses of hygromycin B-resistant calli, regenerated plants and their progeny showed that the introduced Ds was trans-activated by the Ac transposase gene in rice. (1) Cotransfection of the two plasmids is necessary for generation of hygromycin B resistant transformants. (2) Ds excision sites are detected by Southern blot hybridization. (3) Characteristic sequence alterations are found at Ds excision sites. (4) Newly integrated Ds is detected in the rice genome. (5) Generation of 8 bp target duplications is observed at the Ds integration sites on the rice chromosomes. Our results also show that Ds can be trans-activated by the transiently expressed Ac transposase at early stages of protoplast culture and integrated stably into the rice genome, while the cotransfected Ac transposase gene is not integrated. Segregation data from such a transgenic rice plant carrying no Ac transposase gene showed that four Ds copies were stably integrated into three different chromosomes, one of which also contained the functional hph gene restored by Ds excision. The results indicate that a dispersed distribution of Ds throughout genomes not bearing the active Ac transposase gene can be achieved by simultaneous transfection with Ds and the Ac transposase gene.

Effect of insulin on adipocyte lipolysis in exercise-trained rats

The effect of exercise training on the antilipolytic action of insulin was studied in rat adipocytes. Exercise training enhanced lipolysis induced by norepinephrine. Insulin dose dependently inhibited norepinephrine- (1 microM) stimulated lipolysis in both groups. Its inhibition rate was significantly greater in the trained than in the control group. Thus, exercise training enhanced the antilipolytic action of insulin. In the control group, insulin (1,000 microU/ml) reduced the displacement rate of [3H]CGP-12177 binding to adipocytes by low concentrations of (-)-norepinephrine. The slope factor without insulin was 0.76, whereas that with insulin was 0.95. In the trained group, insulin did not affect the competition binding of (-)-norepinephrine for [3H]CGP-12177. The displacement rate of [3H]CGP-12177 binding from adipocytes by low concentrations of (-)-norepinephrine was significantly greater in the trained than in the control group. The number of surface beta-adrenergic receptors per adipocyte was smaller in the trained than in the control group. Cilostamide, which blocks the antilipolytic action of insulin, restored lipolysis in both groups. The recovery rate was significantly greater in the trained than in the control group. These findings suggest that the enhanced antilipolytic action by insulin in the trained group occurs at a site distal to the binding of norepinephrine to beta-adrenergic receptors and that it is due to the increased activity of particulate low-Michaelis constant phosphodiesterase.

No development of tolerance to the hypotensive effect of KRN2391, a novel vasodilator containing a nitrate moiety

The present studies were performed to examine whether tolerance develops to the hypotensive effects of KRN2391, N-cyano-N'-(2-nitroxyethyl)-3-pyridinecarboximidamide monomethanesulfonate. Rats were administered KRN2391 (0.3 or 1 mg/kg, s.c.) or nitroglycerin (10 mg/kg, s.c.) three times a day for 1 to 8 days and blood pressure was then measured under anesthesia. Chronic pretreatment with nitroglycerin attenuated the decrease in blood pressure induced by i.v. nitroglycerin but not that by i.v. KRN2391. Chronic pretreatment with KRN2391 (0.3 or 1 mg/kg, s.c.) had no effect on the decreases in blood pressure induced by i.v. nitroglycerin or i.v. KRN2391. It can be concluded that, in this rat model, no tolerance develops to the hypotensive effects of KRN2391.

Plant bZIP protein DNA binding specificity

Plant bZIP proteins exhibit a relaxed DNA-binding specificity for DNA sequence motifs containing an ACGT core. Gel mobility shift experiments employing ten different recombinant plant bZIP proteins demonstrated that nucleotides flanking the ACGT core affected binding specificity and identified three different types of ACGT elements: G-box, CACGTG; C-box, GACGTC; and A-box, TACGTA, motifs. These ten different bZIP proteins could be categorized into three groups according to their qualitative and quantitative specificity for G-box and C-box elements. Dissociation constant values (Kd values) of these bZIP proteins for high affinity G-box and C-box elements and reciprocal competition gel mobility shift assays confirmed our classification scheme. Group 1 proteins exhibit a stronger binding affinity for G-box elements, group 2 proteins bind both G-box and C-box motifs with comparable binding affinity, whereas the group 3 proteins display a stronger binding affinity for C-box oligonucleotides. Studies using a panel of G-box and C-box oligonucleotides differing in their flanking sequences identified high affinity binding sites. All ten plant bZIP proteins examined, except TGA1a, exhibited type A G-box binding activity preferring class I G-box elements. In contrast to the situation observed for G-box elements, C-box motifs displayed a very much more stringent flanking nucleotide requirement for binding activity. Protein/DNA binding experiments using scanning mutants of a high affinity G-box element and G-box/C-box hybrid elements demonstrated that bZIP protein binding activity depends upon the affinity of protein dimer subunits for ACGT half-sites. Information provided by our systematic analysis of plant bZIP DNA binding specificity can be used to identify high affinity binding sites for the plant bZIP proteins studied here. Assuming that only high affinity bZIP binding sites are likely to function in vivo, identification of these sites will allow us to predict which genes are activated by a particular bZIP protein.

Intralysosomal pH and release of lysosomal enzymes in the rat liver after exhaustive exercise

The mechanism underlying exhaustive exercise-induced release of lysosomal enzymes was studied in the rat liver. Exhaustive exercise resulted in the release of beta-glucuronidase and cathepsin D, but not beta-glucosidase and acid phosphatase, into the blood and cytosol, suggesting that the release of lysosomal enzymes is not due to disruption of lysosomal membranes. The intralysosomal pH of the liver, which was approximately 5.5 at the resting level, rose significantly after exhaustive exercise to pH 6.3. In vitro, beta-glucuronidase and cathepsin D were released at an intralysosomal pH exceeding 6.2. In contrast, beta-glucosidase and acid phosphatase were not released. The elevation of intralysosomal pH reduced the aggregation of beta-glucuronidase and cathepsin D. The rate of ammonia accumulation increased markedly in the lysosome-enriched subcellular fraction after exercise. There was a positive relationship between the rate of ammonia accumulation and the elevation of intralysosomal pH in vitro. Lysosomes isolated after exhaustive exercise showed significantly increased osmotic fragility. Our findings suggest that, during exhaustive exercise, the accumulation of ammonia in lysosomes leads to the elevation of intralysosomal pH, resulting in the reduced aggregation of certain lysosomal enzymes. Thus, less aggregated lysosomal enzymes may be released into the cytosol through the lysosomal membrane, the permeability of which has been increased.

Effect of running training on uncoupling protein mRNA expression in rat brown adipose tissue

The effect was investigated of endurance training on the expression of uncoupling protein (UCP) mRNA in brown adipose tissue (BAT) of rats. The exercised rats were trained on a rodent treadmill for 5 days per week and a total of 9 weeks. After the training programme, a marked decrease in BAT mass was found in terms of weight or weight per unit body weight; there was a corresponding decrease in DNA content and a downward trend in RNA and glycogen levels. The UCP mRNA was present at a markedly decreased level in BAT of trained animals. In consideration of the reduced levels of mRNAs for hormone-sensitive lipase and acyl-CoA synthetase, the brown adipose tissue investigated appeared to be in a relatively atrophied and thermogenically quiescent state.

Comparison of the anti-vasoconstrictor effects of a novel vasodilator KRN2391, nicorandil and nifedipine on isolated porcine large coronary artery

The anti-vasoconstrictor profile of KRN2391, a novel vasodilator, was compared with that of nicorandil and nifedipine in isolated porcine large coronary arteries contracted by KCl, noradrenaline, serotonin, acetylcholine, endothelin-1 and U46619, a thromboxane A2 analogue. KRN2391 (10(-8) - 3 x 10(-5) M), nicorandil (10(-7) - 3 x 10(-4) M) and nifedipine (10(-10) - 10(-5) M) inhibited these contractile responses in a concentration-dependent manner. KRN2391 and nicorandil completely abolished these contractile responses at their maximum effects. However, nifedipine caused less inhibition than KRN2391 and nicorandil and did not completely abolish the contractile responses. The relaxant activity of KRN2391 was more potent than that of nicorandil. This study shows that the anti-vasoconstrictor profiles of KRN2391, nicorandil and nifedipine involve different relaxant mechanisms.

Recovery of beta-receptors and adenylate cyclase from desensitization induced by short term heat exposure in rat parotid glands

1. The recovery of rat parotid beta-adrenergic receptors (beta-AR) and adenylate cyclase (AC) from heat (33 degrees C)-induced desensitization was studied. 2. Down-regulated cell surface beta-AR and AC activity in response to isoprenaline (IPR) returned to the control level 120 hr after the termination of heat exposure. 3. However, beta-AR in parotid crude membranes increased over the control level for 48-120 hr. 4. Coupling between beta-AR and G protein(s) was attenuated at 120 hr. 5. These data suggest that beta-AR on the cell surface, but not those internalized, can transduce biological responses.

Effect of endurance training on angiogenic activity in skeletal muscles

The effect of endurance training on angiogenic activity in skeletal muscle was investigated using cell culture. The exercised rats were trained on a rodent treadmill, 5 days a week for 9 weeks. After the training program, a significant increase (7.8%) in mass was found in soleus muscle (MS), although we noted no apparent increase in gastrocnemius muscle and extensor digitorum longus muscle. The extracts from all the muscles (especially from the MS) of trained rats considerably increased the capillary growth in an in vitro angiogenesis model, in which microvascular fragments and myofibroblastic (Mf) cells isolated from lipid tissues were grown in co-culture. In addition, the extract from the MS of trained rats increased the DNA synthesis and growth of bovine capillary endothelial (BCE) cells, although the extract did not stimulate the growth of Mf cells. Moreover, the extract from the MS of trained rats notably enhanced the activity of plasminogen activator in the conditioned medium of BCE cells compared with that of sedentary rats. On the other hand, extracts from the MS of both sedentary and trained rats increased the synthesis of collagen by Mf cells and metalloproteinase activity in the conditioned medium of BCE cells to the same degree. These results suggest that endurance training increases the angiogenic activity in skeletal muscles.

Genetically engineered rice resistant to rice stripe virus, an insect-transmitted virus

The coat protein (CP) gene of rice stripe virus was introduced into two japonica varieties of rice by electroporation of protoplasts. The resultant transgenic plants expressed the CP at high levels (up to 0.5% of total soluble protein) and exhibited a significant level of resistance to virus infection. Plants derived from selfed progeny of the primary transformants also expressed the CP and showed viral resistance, indicating stable transmission of the CP gene and the trait of resistance to the next generation. Moreover, the virally encoded strip disease-specific protein was not detected in transgenic plants expressing CP 8 weeks after inoculation, indicating protection before viral multiplication. These studies demonstrated that CP-mediated resistance to virus infection can be extended to cereals and to the viruses transmitted by an insect vector (planthopper).

Phorbol ester alters carbachol-stimulated diacylglycerol formation in parotid acinar cells through the hydrolysis of phosphoinositides and phosphatidylcholine

Incubation of rat parotid acinar cells with phorbol 12,13-dibutyrate (PDBu) resulted in inhibition of carbachol-stimulated formation of sn-1,2-diacylglycerol (DAG). PDBu pretreatment inhibited carbachol-induced turnover of phosphoinositides; this inhibition was indicated by phosphatidylinositol 4,5-bisphosphate breakdown. This pretreatment also attenuated the effect of carbachol on inositol phosphate generation and phosphatidylcholine hydrolysis. These results show that PDBu alters carbachol-stimulated DAG formation through the hydrolysis of phosphoinositides and phosphatidylcholine.

Ca2+ ionophore and phorbol ester stimulate diacylglycerol formation and phosphatidylcholine hydrolysis in rat parotid acinar cells

We investigated the effects of A23187 and phorbol 12,13-dibutyrate (PDBu) on sn-1,2-diacylglycerol (DAG) accumulation and phosphatidylcholine (PC) hydrolysis in rat parotid acinar cells. Both A23187 and PDBu, in concentration ranges of 0.001-0.1 microM, stimulated DAG accumulation and PC hydrolysis in a time- and concentration-dependent manner. Treatment with A23187 and PDBu stimulated the release of [3H]choline and [3H]phosphocholine into the medium, indicating [3H]PC hydrolysis is due to the activation of phospholipases C and D; however, [3H]phosphatidylethanolamine hydrolysis was not indicated. These releases were unaffected by the addition of glucose 6-phosphate, a phosphatase inhibitor. Staurosporine, a protein kinase C inhibitor, significantly inhibited the DAG accumulation and the PC hydrolysis stimulated by these agents. Combinations of A23187 and PDBu potentiated the stimulatory effect which each of these agents alone had on DAG accumulation and PC hydrolysis. This mode of action was additive but not synergistic. These results suggest that DAG accumulation induced by A23187 and PDBu is related to the PC hydrolysis mediated via the activation of phospholipases C and D, and that it is not related to phosphatidylethanolamine hydrolysis.

Ca2+ potentiates corticotropin-induced, but not isoproterenol-induced, [3H]guanosine diphosphate release in rat adipocyte membranes

EGTA abolished corticotropin (ACTH)-stimulated adenylate cyclase in rat adipocyte membranes. In contrast, the potency of guanosine triphosphate (GTP) stimulation of adenylate cyclase activated with ACTH was greater in the presence of Ca2+ (1 mmol/L). EGTA (1 mmol/L) powerfully inhibited ACTH-stimulated [3H]guanosine diphosphate (GDP) release from membranes prelabeled with [3H]GTP in the presence of isoproterenol (ISO) or ACTH, whereas Ca2+ significantly increased it. In contrast, neither EGTA nor Ca2+ affected ISO-stimulated [3H]GDP release. These data clearly show that Ca2+ is necessary for the binding of ACTH to its receptor, and that Ca2+ stimulates the interaction of the ACTH-occupied receptor with GTP-binding proteins.

Ovarian juvenile granulosa cell tumor associated with Maffucci's syndrome

A 15-year-old girl developed a juvenile granulosa cell tumor associated with Maffucci's syndrome (enchondromatosis + hemangiomas). Clinical manifestations of the disease included an abdominal mass and progressive anemia. She underwent the removal of a Stage Ic juvenile granulosa cell tumor and subsequent adjuvant chemotherapy. On follow-up examination 4 years later, no recurrence of the ovarian tumor was noted. A review of the literature showed 10 previous cases of juvenile granulosa cell tumor associated with enchondromatosis, two associated with Maffucci's syndrome, and the rest with Ollier's disease (enchondromatosis). Ovarian juvenile granulosa cell tumor may occur not infrequently in female patients with enchondromatosis in the first or second decades, in contrast to the widely recognized sarcomatous changes of enchondromas that usually occur after the second decade. Data provided from these cases also emphasize the concept of a generalized mesodermal dysplasia.

Mechanism of carbachol-stimulated diacylglycerol formation in rat parotid acinar cells

We studied the relationship between phosphoinositide hydrolysis, phosphatidylcholine hydrolysis, and sn-1,2-diacylglycerol (DAG) formation in response to carbachol stimulation in rat parotid acinar cells. Previously, we demonstrated that DAG formation stimulated with 1 microM carbachol was biphasic: the first peak occurred at 5 min and the second one at 20 min. It was also demonstrated that the second peak was regulated in part by a calmodulin/protein kinase C-dependent mechanism. Based on the kinetic analysis of DAG formation and [32P]phosphoinositide breakdown, the first peak of carbachol (1 microM)-stimulated DAG accumulation was found to be related to the breakdown of [32P]phosphatidylinositol 4-monophosphate ([32P]PIP) and [32P]phosphatidylinositol 4,5-bisphosphate ([32P]PIP2). The second peak was found to be related to [32P]PIP2 breakdown. Carbachol stimulated the release of [3H]phosphocholine into the medium, indicating that the predominant pathway for phosphatidylcholine hydrolysis was via phospholipase C. Moreover, carbachol stimulated the release of [3H]choline metabolites in a time- and dose-dependent manner. This agonist slightly stimulated the release of [3H]ethanolamine metabolites. A calmodulin/protein kinase C-dependent mechanism was also studied and was found to be involved in carbachol-stimulated phosphatidylcholine hydrolysis; W-7, a calmodulin inhibitor and staurosporine, a protein kinase C inhibitor, inhibited the carbachol (1-microM)-induced release of [3H]choline metabolites at 20 min in a dose-dependent manner, but did not have inhibitory effects at 5 min. These results suggest that the first peak of DAG accumulation induced by carbachol is predominantly associated with the breakdown [32P]PIP and of [32P]PIP2 and that the second peak is predominantly associated with [32P]PIP2 breakdown and phosphatidylcholine hydrolysis.

Substance P-induced diacylglycerol formation in rat parotid acinar cells

The mechanisms underlying the ability of substance P, to stimulate the sn-1,2-diacylglycerol (DAG) formation were studied using rat parotid acinar cells. During a 60 s stimulation, 1 microM substance P caused a rapid rise in DAG accumulation at 5 s, whereas a low (0.1 microM) concentration of agonist did not. During long term stimulation for 30 min, DAG accumulation induced by 1 microM substance P reached near maximal levels at 5 min and remained elevated for at least 20 min. In contrast, DAG formation induced by 0.1 microM substance P exhibited a peak at 5 min, gradually declined and returned to near basal levels at 30 min. Furthermore, DAG accumulation in response to substance P at 5 and 20 min increased in a dose-dependent manner. The breakdown of both [32P]phosphatidylinositol 4-monophosphate ([32P]PIP) and [32P]phosphatidylinositol 4,5-bisphosphate ([32P]PIP2) stimulated by 1 microM substance P significantly increased from 5 to 20 min and returned to basal levels by 30 min; however, the breakdown of [32P]PIP2 was greater than that of [32P]PIP. At a low concentration of substance P, [32P]PIP2 breakdown reached maximal levels at 5 min followed by a progressive decrease and returned to basal levels at 30 min, whereas the breakdown of [32P]PIP reached maximal levels at 5 min and returned to near basal levels at 10 min. Both concentrations of substance P caused some [32P]phosphatidylinositol breakdown at 5 min. Changes in [3H]inositol trisphosphate induced by substance P were similar to those in [32P]PIP2. In addition, substance P (1 microM) did not stimulate the release of [3H]choline or [3H]ethanolamine metabolites into the medium. Substance P-induced DAG formation was not inhibited by staurosporine, a protein kinase C inhibitor. These results suggest that DAG formation caused by substance P is closely associated with the hydrolysis of phosphatidylinositides but not that of phosphatidylcholine or phosphatidylethanolamine, and is not regulated by protein kinase C-dependent mechanism(s).

Anaerobic induction and tissue-specific expression of maize Adh1 promoter in transgenic rice plants and their progeny

In order to analyze expression of the maize alcohol dehydrogenase 1 gene (Adh1), its promoter was fused with the gusA reporter gene and introduced into rice by protoplast transformation. Histochemical analysis of transgenic plants and their progeny showed that the maize Adh1 promoter is constitutively expressed in root caps, anthers, anther filaments, pollen, scutellum, endosperm and shoot and root meristem of the embryo. Induction of expression by the Adh1 promoter was examined using seedlings derived from selfed progeny of the transgenic plants. The results showed that expression of the Adh1 promoter was strongly induced (up to 81-fold) in roots of seedlings after 24 h of anaerobic treatment, concomitant with an increase in the level of gusA mRNA. 2,4-D also induced Adh1 promoter-directed expression of gusA to a similar extent. In contrast, little induction by anaerobic treatment was detected in transformed calli, leaves or roots of primary transformants or shoots of seedlings. A detailed examination of seedling roots during anaerobic treatment revealed that the induction started first at the meristem and after 3 h there was strong induction in the elongation zone which is located 1-2 mm above the meristem; the induction then progressed upward from this region. Our results suggest that transgenic rice plants carrying the gusA reporter gene fused with promoters are useful for the study of anaerobic regulation of genes derived from graminaceous species.

Protein kinase C-dependent diacylglycerol formation is mediated via Ca2+/calmodulin in parotid cells

The kinetics of carbachol-induced sn-1,2-diacylglycerol (DAG) formation and the underlying mechanism(s) involved in parotid acinar cells were investigated. Supramaximal concentrations of carbachol for amylase secretion (10 microM) caused a transient rise in DAG levels at 10 s. In contrast, this rapid rise was not elicited by 1 microM carbachol, which is the maximally effective concentration for amylase secretion. Carbachol (10 microM) also increased DAG levels linearly up to 20 min, which were sustained for up to a further 10 min. DAG formation stimulated by 1 microM carbachol was biphasic; the first peak was observed after 5 min and the second after 20 min. DAG formation induced by 0.01-0.1 microM carbachol was concentration-dependent and monophasic, peaking at 5 min. The second peak evoked by carbachol was partly inhibited by Ca2+ deprivation from the extracellular space, whereas the first peak was not. Similar results were obtained in experiments using Ca2+ antagonists such as verapamil and LaCl3. The protein kinase C inhibitors, 1-(5-isoquinolinesulfonyl)-2-methylpiperazine (H-7) and staurosporine, and a calmodulin antagonist, N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide (W-7), significantly inhibited the second DAG peak produced by 1 microM carbachol, but did not alter the first peak. The degree of inhibition of the second peak by these antagonists was comparable. Furthermore, the inhibitory effect of staurosporine and W-7 was concentration-dependent. The A23187-induced accumulation of DAG also was abolished by both staurosporine and W-7. These data indicate that a protein kinase C-dependent mechanism(s) is involved in mediating the second DAG accumulation peak induced by 1 microM carbachol and is mainly regulated by the Ca(2+)-calmodulin complex.

Introduction and transposition of the maize transposable element Ac in rice (Oryza sativa L.)

To develop a transposon tagging system in an important cereal plant, rice (Oryza sativa L.), the maize transposable element Ac (Activator) was introduced into rice protoplasts by electroporation. We employed a phenotypic assay for excision of Ac from the selectable hph gene encoding resistance to hygromycin B. Southern blot analysis of hygromycin B-resistant calli showed that the Ac element can transpose from the introduced hph gene into the rice chromosomes. Sequence analysis of several Ac excision sites in the hph genes revealed sequence alterations characteristic of the excision sites of this plant transposable element. The Ac element appears to be active during development of transgenic rice plants from calli. Moreover, hybridization patterns of different leaves from the same plant indicated that some Ac elements are stable whereas others are able to transpose further during development of leaves. The results indicate that the introduced Ac element can transpose efficiently in transgenic rice plants.

Enhanced coupling of adenylate cyclase to lipolysis in permeabilized adipocytes from trained rats

Digitonin-permeabilized adipocytes were used to study the coupling of adenylate cyclase (AC) to lipolysis in exercise-trained rats. Isoproterenol-(IPR) stimulated lipolysis in permeabilized cells was significantly greater in trained than in control rats. Under essentially identical conditions, the dose-response curve for IPR stimulation of AC activity in the absence of 3-isobutyl-1-methylxanthine was similar in trained and control rats. However, the potency of stimulation by IPR as a percentage of the basal level was greater in trained rats. AC activity and lipolysis in the presence of 3-isobutyl-1-methylxanthine were also significantly greater in trained than in control rats. Least-squares analysis by plotting the log AC vs. lipolysis values showed that the regression coefficient was about three-fold greater in trained than in control rats. The concentration of endogenous adenosine 3',5'-cyclic monophosphate (cAMP) needed to produce a half-maximal lipolytic response was 18.58 and 10.81 pmol.min-1.10(6) cells-1 in control and trained rats, respectively. Thus a positive relationship existed between lipolysis and AC activity, with a tighter coupling in trained rats. Lipolysis in response to exogenous cAMP tended to be greater in trained than in control rats, and the difference was statistically significant for 50 microM and 10 mM cAMP. Our finding support the concept that the major mechanism of enhanced lipolysis in trained rats was an increase in the activity of enzymatic step(s) distal to cAMP.

Characteristics of KRN2391, a novel vasodilator, compared with those of cromakalim, pinacidil and nifedipine in rat aorta

The characteristics of KRN2391, a novel vasodilator, were studied in rat isolated aorta. The effects of KRN2391, cromakalim, pinacidil and nifedipine on the contractions induced by 20, 40 and 80 mM K+ and by 10(-7) M norepinephrine (NE) were measured first. KRN2391, cromakalim and pinacidil selectively inhibited the contractions induced by 20 mM K+ and NE rather than those induced by high concentrations of K+. Nifedipine could not completely inhibit the NE-induced contractions. The vasorelaxant effect of KRN2391 was inhibited by K+ channel blockers and guanylate cyclase inhibitors. KRN2391, cromakalim and pinacidil increased the 86Rb efflux rate coefficient. Thus, KRN2391 exhibits a vasodilator profile similar to that of the K+ channel openers and induces an increase in 86Rb efflux. It is suggested that opening of the membrane K+ channels may be partly involved in the vasorelaxant mechanism of KRN2391.

In vivo adaptive control of beta-receptors and adenylate cyclase during short-term heat exposure in rat parotid glands

1. Adaptation of beta-adrenergic receptors (beta-AR) and adenylate cyclase (AC) in rat parotid glands during short-term heat exposure (33 degrees C) were studied. 2. Heat exposure reduced AC activity in response to isoproterenol (IPR). 3. The number of beta-AR on the cell surface significantly increased after 24 hr but returned to control level after 48 hr. 4. IPR-induced [3H]GDP release was significantly reduced throughout exposure. 5. The data suggest that the major factor which results in the desensitization of AC during short-term heat exposure is a blunted coupling between beta-AR and GTP binding protein(s).

Screening for bacteriuria in Japanese school children

Bacteriuria was screened among 28,202 healthy school children, 14,575 boys and 13,627 girls, by dipstick and dipslide methods and also by pour plate culture. The prevalence of bacteriuria was 0.06% in boys and 0.52% in girls after the third screening. A high rate of false negative results with the dipstick test and a high rate of false positive results with the dipslide culture method using Microstix-3 were observed. About 60% of screened children continued to have bacteriuria persistently for 9 months after the third screening, which was followed by monthly urine cultures. Anomalies of the urinary tract were detected in 9 of 26 children with persistent bacteriuria.