Involvement of Rho kinase in the pathogenesis of acute pulmonary embolism-induced polystyrene microspheres in rats

Acute pulmonary embolism (PE) is a life-threatening disease, and several vasoconstrictors, including endothelin-1 (ET-1), play a key role in vasoconstriction and hypoxemia during the development of PE. Rho kinase is activated by various vasoconstrictors resulting in vascular contraction and remodeling. Recent evidence has revealed an important role of Rho kinase in the pathogenesis of systemic and pulmonary vascular diseases. However, contribution of Rho kinase in PE remains unclear. We thus investigated the role of Rho kinase in the PE rat model induced by intrajugular administration of polystyrene microspheres (mean diameter, 26 microm). At 6 h following the administration of microspheres (1.5 ml/kg), right ventricular systolic pressure (RVSP) was higher in the PE than in the control rats (15.8 +/- 1.6 vs. 32.9 +/- 7.5 mmHg). Arterial oxygen tension was lower (92.3 +/- 12.5 vs. 66.0 +/- 17.7 Torr), and alveolar-arterial difference in oxygen partial pressure was higher (3.9 +/- 3.8 vs. 36.5 +/- 26.9 Torr) in the PE rats. Western blotting analysis revealed upregulation and downregulation in expression of vascular cell adhesion molecule-1 and endothelial nitric oxide synthase in lungs from the PE rats, respectively, and radioimmunoassay demonstrated an increase in plasma ET-1 levels. Lung Rho kinase alpha expression was greater in the PE rats. At 5 h following administration of microspheres (0.75 ml/kg), intravenous Rho kinase inhibitors HA1077 and Y27632 (3 mg/kg each) attenuated elevation of RVSP (22.0 +/- 3.7, 17.1 +/- 3.2, 14.3 +/- 2.6 mmHg, PE, PE+HA1077, PE+Y27632) and the severity of hypoxemia (66.3 +/- 16.2, 94.9 +/- 23.0, 89.1 +/- 8.5 Torr, PE, PE+HA1077, PE+Y27632) in the PE rats. These results suggest that pulmonary endothelial dysfunction and activation of Rho kinase may contribute to the potentiation of vasoconstriction and hypoxemia in the PE rats.

RASSF2, a potential tumour suppressor, is silenced by CpG island hypermethylation in gastric cancer

RASSF2, a member of the RASSF1 family, has recently been identified as a potential tumour suppressor. We examined methylation status in multiple regions which included the CpG island and spanned the transcription start site of RASSF2 in 10 gastric cancer cell lines, as well as 78 primary gastric cancers and corresponding non-neoplastic gastric epithelia. Hypermethylation of RASSF2 in at least one of the regions examined was detected in seven (70%) of the 10 cell lines; two (20%) exhibited hypermethylation in all the regions examined including the transcription start site and lost expression of RASSF2 mRNA, which could, however, be restored by 5-aza-2′ deoxycytidine treatment, while the other five (50%) cell lines exhibited hypermethylation at the 5′- and/or 3′- edge, with four of them expressing RASSF2 mRNA. In primary gastric cancers and corresponding non-neoplastic gastric epithelia, frequencies of RASSF2 methylation ranged from 29% (23 out of 78) to 79% (62 out of 78) and 3% (two out of 78) to 60% (47 out of 78), respectively, at different CpG sites examined. Methylation was frequently observed at the 5′- and 3′- edges, and became less frequent near the transcription start site in both the primary gastric cancers and corresponding non-neoplastic gastric epithelia. Hypermethylation near the transcription start site was mostly cancer-specific. We thus showed that RASSF2 is silenced by hypermethylation near the transcription start site in gastric cancer. Hypermethylation was found initially to occur at the 5′- and 3′- furthest regions of the CpG island in non-neoplastic gastric epithelia, to gradually spreads near the transcription start site to shut down RASSF2 expression, and ultimately to constitute a field-defect placing tissue increased risk for development of gastric cancer.

Electrophysiologic effects of an antiarrhythmic agent, bidisomide, on sodium current in isolated rat ventricular myocytes: comparison with mexiletine and disopyramide

The effects of bidisomide, an antiarrhythmic agent, on sodium current (I(Na)) in isolated rat ventricular myocytes were investigated using a whole cell voltage clamp method. Bidisomide blocked I(Na) with a Ki of 214 microM at a holding potential of -140 mV. The blockade of I(Na) was enhanced at a less negative holding potential of -100 mV with a Ki of 21 microM. Bidisomide shifted the steady state inactivation curve to a negative potential direction by 20 mV without a significant change in the slope factor. Bidisomide slowed the time course of recovery of I(Na) at a holding potential of -140 mV with a slow recovery phase. The time constant of recovery phase for bidisomide, disopyramide and mexiletine were 2703, 1858 and 757 ms, respectively. The development of the block of I(Na) consisted of two phases in the presence of bidisomide. The fast and slow time constants were 11 and 648 ms. Bidisomide produced a use-dependent block of I(Na) when the depolarizing pulse was repeated at 1-3 Hz. Our results indicate that bidisomide binds to rat cardiac sodium channels and that the dissociation kinetics of bidisomide from the inactivated sodium channel is slower than that of disopyramide.

Both alpha(1A)- and alpha(1B)-adrenergic receptor subtypes couple to the transient outward current (I(To)) in rat ventricular myocytes

1. Regulation of transient outward current (I(To)) by alpha(1)-adrenergic (alpha(1)AR) plays a key role in cardiac repolarization. alpha(1)ARs comprise a heterogeneous family; two natively expressed subtypes (alpha(1A) and alpha(1B)) and three cloned subtypes (alpha(1a), alpha(1b) and alpha(1d)) can be distinguished. We have examined the electrophysiological role of each alpha(1)AR subtype in regulating I(To) in isolated rat ventricular myocytes. 2. Reverse transcription-PCR study revealed the presence of three subtype mRNAs (alpha(1a), alpha(1b) and alpha(1d)) in rat myocytes. 3. Radioligand binding assay using [(125)I]-HEAT showed that the inhibition curves for alpha(1A)AR-selective antagonists (WB4101, 5-methylurapidil, (+)-niguldipine and KMD-3213) in rat ventricles best fit a two-site model, with 30% high and 70% low affinity binding sites. The high affinity sites were resistant to 100 microM chloroethylclonidine (CEC), while the low affinity sites were highly inactivated by CEC. 4. Whole cell voltage clamp study revealed that methoxamine reduced a 4-aminopyridine(4-AP)-sensitive component of I(To) in the isolated rat ventricle myocytes. Lower concentrations of KMD-3213 (1 nM) or 5-MU (10 nM) did not affect the methoxamine-induced reduction of I(To). On the other hand, CEC treatment (100 microM) of isolated myocytes reduced the methoxamine-induced reduction of I(To) by 46%, and the remaining response was abolished by lower concentrations of KMD-3213 or 5-MU. 5. The results indicate that rat ventricular myocytes express transcripts of the three alpha(1)AR subtypes (alpha(1a), alpha(1b) and alpha(1d)); however, two pharmacologically distinct alpha(1)AR subtypes (alpha(1A) and alpha(1B)) are predominating in receptor populations, with approximately 30% alpha(1A)AR and 70% alpha(1B)AR. Although both alpha(1A) and alpha(1B)AR subtypes are coupled to the cardiac I(To), alpha(1B)ARs predominantly mediate alpha(1)AR-induced effect.

The anti-ischemic effects of CP-060S during pacing-induced ischemia in anesthetized dogs

CP-060 S, (-)-( S)-2-[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]-3-[3-[N-methyl-N-[2-(3 ,4-methylenedioxyphenoxy)ethyl]-amino]propyl]-1,3-thiazolidin++ +-4-one hydrogen fumarate, is a novel cardioprotective drug which prevents Na+-, Ca2+-overload and has Ca2+ channel blocking activity. We compared the anti-ischemic effects of CP-060S with those of diltiazem, a Ca2+ channel blocker, and R56865, N-[1-[4-(4-fluorophenoxy)butyl]-4-piperidinyl]-N-methyl-2-benzothiazo lamine, a Na+-, Ca2+-overload inhibitor, in a canine pacing-induced ischemia model. CP-060S 100 microg kg(-1) significantly suppressed the pacing-induced ischemic epicardial ST-segment elevation by maximally 75%, while diltiazem 100 microg kg(-1) suppressed it by maximally 35%. R56865 100 microg kg(-1) significantly suppressed the ST-segment elevation by maximally 30%. In addition, diltiazem 100 microg kg(-1) caused synergistic suppression of ST-segment elevation by 70% when administered simultaneously with R56865 100 microg kg(-1). These results suggest that a Na+-, Ca2+-overload preventive action and a Ca2+ channel blocking action independently contribute to the suppression of the ST-segment elevation. Therefore, CP-060S may suppress pacing-induced ST-segment elevation by a dual action by preventing Na+-, Ca2+-overload and the Ca2+ channel blockade.

A particle-receptor model for the insulin-induced closure of connexin43 channels

Connexin43(Cx43) channels can be regulated by a variety of factors, including low pHi. Structure/function studies from this laboratory have demonstrated that pH gating follows a particle-receptor mechanism, similar to the "ball-and-chain" model of voltage-dependent inactivation of ion channels. The question whether the particle-receptor model is applicable only to pH gating or to other forms of Cx43 regulation as well remains. To address this question, we looked at the uncoupling effects of insulin and of insulin-like growth factor-1 (IGF) on Cx43 channels expressed in Xenopus oocytes. These agonists do not induce changes in pHi. Junctional conductance (Gj) was measured by the dual 2-electrode voltage-clamp technique. Control studies showed that relative Gj did not change spontaneously as a function of time. Continuous exposure of Cx43-expressing oocytes to insulin (10 micro/L) led to a decrease in Gj. After 80 minutes, Gj was 54+/-5% from control (n= 12). Exposure of oocytes to IGF (10 nmol/L) caused an even more pronounced change in Gj (37+/-4% of control, n=6). The time course of the IGF-induced uncoupling was similar to that observed after insulin exposure. The effect of insulin was abolished by truncation of the carboxyl-terminal domain of Cx43 at amino acid 257 (M257). Interestingly, as in the case of pH gating, coexpression of the carboxyl-terminal domain (amino acids 258 to 282) together with M257 rescued the ability of insulin to reduce coupling (Gj, 39+/-12% from control; n=6). Structure/function experiments using various deletion mutants of the carboxyl-terminal domain showed that insulin treatment does not modify Gj if amino acids 261 to 280 are missing from the Cx43 sequence. Our results suggest that a particle-receptor (or ball-and-chain) mechanism, similar to that described for pH gating, also applies to chemical regulation of Cx43 by other factors.

Flow cytometry analysis of alpha1-adrenoceptor subtypes

To characterize the alpha1-adrenoceptor subtypes, we developed a flow cytometry method using the fluorescent ligand BODIPY-FL prazosin and the anti-peptide antibody against the alpha1b-adrenoceptor amino terminus (designated 1B-N1-C) as probes. Three alpha1-adrenoceptors (alpha1a, alpha1b and alpha1d) expressed in CHO cells were detected by BODIPY-FL prazosin; however, only alpha1b-adrenoceptor subtype was detected by the anti-peptide antibody 1B-N1-C. Furthermore, the flow cytometry analysis with 1B-N1-C specifically identified alpha1b-adrenoceptor in native cells of hamster DDT1-MF2 cells, rat hepatocytes and cardiomyocytes.

Long-term complications of dialysis: pathogenic factors with special reference to amyloidosis

Amyloidosis, caused by amyloid containing beta 2-microglobulin (beta 2m), is a frequent complication of long-term hemodialysis. The precise mechanism of its pathogenesis is not known. While beta 2m is an amyloid protein, other factors likely are involved in the pathogenesis of such amyloidosis. In treating patients with dialysis-related amyloidosis, it is essential to remove as much beta 2m from the blood as possible. In this respect, progress has been made in developing a column to adsorb beta 2m from the blood. Using a combination of a high-flux dialyzer and an adsorption column, it becomes possible to efficiently eliminate beta 2m. We have treated four patients with this column in combination with a high-flux dialyzer three times a week for periods of one month or one year. The absorbent column eliminates beta 2m from the blood, and may thus halt or slow the progression of beta 2m-related amyloidosis. However, such treatment is still in a preliminary phase; long-term studies are required to determine clinical efficacy.

A new therapeutic approach to dialysis amyloidosis: intensive removal of beta 2-microglobulin with adsorbent column

Amyloidosis, in which amyloid protein consists of beta 2-microglobulin (beta 2-M), is both a common and a serious complication of long-term hemodialysis. The mechanism of its development is not completely understood. Since beta 2-M is an amyloid protein, it is essential to try to remove as much of it as possible. A specific adsorbent of beta 2-M has been developed for use in direct hemoperfusion. The adsorbent is a porous cellulose bead to which hydrophobic organic compound is bound covalently. A combination of a high-flux membrane dialyzer and an adsorption column (BM-01) would make it possible to efficiently eliminate beta 2-M. Dialysis with a combination of direct hemoperfusion (DHP) and an adsorption column led to the elimination of more than 200-300 mg of beta 2-M. We observed 5 patients who received treatment with this column (BM-01) in combination with high-flux dialysis 3 times a week for periods of 1 week (3 patients), 6 months (1 patient), or 14 months (1 patient). It is demonstrated that the adsorbent column (BM-01) provides an intensive method to eliminate beta 2-M from the blood with no serious adverse effect. It thus has the potential to suppress the progression of dialysis amyloidosis. The use of this adsorbent column (BM-01) in combination with a high-flux dialyzer may present an improved approach to removing beta 2-M from the body.

Cystic radiolucencies of carpal bones, distal radius and ulna as a marker for dialysis-associated amyloid osteoarthropathy

Patients on long-term hemodialysis (HD) are known to develop amyloid osteoarthropathy, evidenced as cystic radiolucencies on X-rays of the affected joints. To study the relationship between cystic radiolucencies and amyloid osteoarthropathy in 394 patients, we classified the severity of the cystic radiolucencies seen in the wrist joint on a 4-point scale and evaluated the association between lesion severity (grade) and several parameters. Biopsy was performed in 8 patients with 11 bone cysts of the wrist joint who had been operated for carpal tunnel syndrome. HD for 10 years or longer, age 50 or older and the presence of carpal tunnel syndrome were associated with severe cyst rating. There was no association between lesion grade and serum level of PTH-C, aluminum or beta 2-microglobulin (B2M). Ten of the 11 biopsied bone cysts in 8 patients with carpal tunnel syndrome demonstrated amyloid deposits which reacted with B2M. We conclude that a cystic radiolucency observed in the wrist joint of a patient undergoing HD indicates the deposition of amyloid. The cyst grade provides a useful marker for the severity of amyloid osteoarthropathy in HD patients.

Anticholinergic action of quinidine sulfate in the rabbit atrioventricular node

Anticholinergic action of quinidine sulfate was electrophysiologically studied by recording spontaneous action potentials and membrane current of the rabbit atrioventricular node. In the presence of 0.1 mumol/l carbachol, the spontaneous activity of the atrioventricular nodal preparations was markedly inhibited, whereas subsequent addition of 1, 5 and 20 mumol/l quinidine restored automaticity in a concentration-dependent manner. In some preparations, quinidine at concentrations of 5 mumol/l and higher slowed the spontaneous activity by its direct membrane action even in the presence of carbachol. The dose-response curve for acetylcholine action on the spontaneous firing frequency showed that one molecule of acetylcholine bound to one muscarinic receptor of the atrioventricular node cell (Hill coefficient = 1.2). A parallel shift of this curve towards higher acetylcholine concentrations was observed at 0.03, 0.1 and 0.3 mumol/l but not at 1 and 3 mumol/l quinidine, suggesting a noncompetitive antagonism of quinidine against acetylcholine. Voltage clamp experiments revealed that 5 mumol/l quinidine reduced the slow inward current, hyperpolarization-activated inward current, and delayed rectifying K+ current, through its membrane actions. Quinidine at this concentration almost completely suppressed the acetylcholine-activated K+ current, which showed a relaxation phenomenon. Hence, the direct blockage of the acetylcholine-activated K+ current by quinidine was considered responsible for the anticholinergic action of this drug. We conclude that quinidine is a non-specific ionic channel blocker that inhibits all the membrane currents in the atrioventricular node including the acetylcholine-activated K+ current.

Electrophysiologic actions of aprindine in rabbit atrioventricular node

Aprindine hydrochloride is a potent antiarrhythmic agent against various atrial and ventricular tachyarrhythmias. To elucidate its pharmacological actions in the atrioventricular node, electrophysiologic experiments were conducted by applying microelectrode and voltage clamp methods to small preparations of the rabbit atrioventricular node. At a concentration 1 mumol/l, aprindine decreased the spontaneous firing frequency, maximal rate of depolarization, action potential amplitude, and take-off potential (P less than 0.05, n = 7). The spontaneous and rate-controlled action potential durations at 50 and 100% repolarization were prolonged by aprindine. Voltage-clamp experiments using the double microelectrode method revealed that aprindine blocked the slow inward current (Isi) in a voltage-dependent manner with a dissociation constant of 10 mumol/l and Hill coefficient of 0.8. The steady-state inactivation curve for Isi was shifted toward more negative potentials by 2.5 +/- 0.9 mV (P less than 0.05, n = 5) without a significant change in the slope factor. This finding suggests that aprindine has a higher affinity for inactivated slow inward (or Ca2+) channels than for resting channels. Aprindine caused use-dependent block of Isi, a result consistent with the drug's slow dissociation from inactivated Ca2+ channels. The delayed rectifying K+ current (IK) tail obtained on repolarization from +10 mV to -60 mV was significantly decreased from 15.4 +/- 2.4 to 6.8 +/- 1.4 nA (P less than 0.01, n = 6) and the deactivation time constant significantly increased by 20.7% (P less than 0.01, n = 6). The steady-state activation curve for IK was shifted in the hyperpolarized direction by 6.9 +/- 2.9 mV, suggesting a potent voltage-dependent block of this current by aprindine. The hyperpolarization-activated inward current (Ih) was decreased from 14.4 +/- 5.4 to 12.0 +/- 5.5 nA (P less than 0.05, n = 5). The transient outward and inward currents induced by 1 mumol/l acetylstrophanthidin were almost completely suppressed after the addition of 1 mumol/l aprindine. These results suggest that aprindine exerts a negative chronotropic action both by slowing deactivation of IK and by reducing Isi and Ih, and delays atrioventricular nodal conduction by reducing Isi and IK. These blocking actions of aprindine together with its inhibition of the transient outward and inward currents may explain its antiarrhythmic effects on the atrioventricular node.

Ionic mechanisms of the depression of automaticity and conduction in the rabbit atrioventricular node caused by hypoxia or metabolic inhibition and protective action of glucose and valine

The effects of hypoxia and a metabolic inhibitor, sodium cyanide (NaCN), on the spontaneous action potential and membrane current systems were studied in small preparations (0.2 x 0.2 x 0.1 mm) of rabbit atrioventricular node. When the PO2 of the superfusate was lowered from 500 to less than 20 mm Hg, all the preparations initially showed reductions in the spontaneous firing frequency (due to the decreased rate of diastolic depolarization) and maximal rate of depolarization, which were followed by a cessation of automatic activity with subsequent membrane hyperpolarization to -57 +/- 3 mV (n = 4). Voltage clamp experiments using double microelectrode techniques revealed that hypoxia reduced the slow inward current by 20 to 80% without affecting its inactivation kinetics. The delayed rectifying potassium current tail was also reduced or abolished by severe hypoxia, whereas the background outward current was greatly increased. The hyperpolarization-activated inward current was decreased by hypoxia. Similar changes in the spontaneous action potential and membrane currents were obtained on adding 0.1 to 0.5 mM NaCN to the superfusate under conditions of normal PO2. Hypoxia-induced suppression of automaticity was reversed completely by 5 mM glucose, and partially by 40 mM valine. These results suggest that (1) hypoxia impairs atrioventricular nodal conduction by reducing the slow inward current and the delayed rectifying potassium current; (2) hypoxia depresses automaticity by increasing the background outward current and, to some extent, by reducing the slow inward current; and (3) glucose and valine contribute to the generation of high-energy phosphates in cytoplasm and mitochondria, respectively, and protect the atrioventricular node from hypoxia.

Augmentation and subsequent attenuation of Ca2+ current due to lipid peroxidation of the membrane caused by t-butyl hydroperoxide in the rabbit sinoatrial node

Cellular electrophysiological effects of membrane lipid peroxidation by t-butyl hydroperoxide (TBH) were studied in the rabbit sinoatrial (SA) node. Superfusion for 1-5 min with 300 microM TBH caused an initial increase and subsequent decrease in the spontaneous firing frequency of the SA node. Voltage clamp experiments revealed that TBH initially enhanced but later blocked the Ca2+ current. Thus, membrane lipid peroxidation appears to accelerate and then suppress physiological automaticity by causing biphasic changes in the Ca2+ current.

Subtypes of muscarinic receptors in pancreatic exocrine secretion in anesthetized dog

Characterization of muscarinic receptor subtypes on the dog pancreas in situ was examined by using specific muscarinic receptor antagonists to study pancreatic exocrine secretion. Bethanechol caused an increase in pancreatic exocrine secretion, with a high concentration of protein and little effect on bicarbonate concentration. Thus bethanechol may mainly affect the muscarinic receptors of the acinar cells. Bethanechol-stimulated secretion was inhibited by pirenzepine (a specific M1 muscarinic antagonist), 4-diphenylacetoxy-N-methylpiperidine methobromide (4-DAMP, a specific M3 muscarinic antagonist), and atropine (a mixed muscarinic receptor antagonist). However, [11-[[2-(diethylamino)methyl]-1-piperidinyl]acetyl]-5, 11- dihydro-6H-pyrido[2,3-b][1,4]benzo-diazepine-6-one (AF-DX 116, a specific cardioselective M2 antagonist) did not have any effects on bethanechol-stimulated secretion. Increased protein secretion in pancreatic juice stimulated by bethanechol was significantly inhibited by 4-DAMP and atropine and was suppressed by pirenzepine, but was not modified by AF-DX 116. Bicarbonate concentration was not modified by these antagonists. 4-DAMP, atropine, and pirenzepine caused a progressive parallel rightward shift in the dose-response curve of pancreatic secretion for bethanechol. Schild analysis of the data indicated a pA2 value of 8.7 for 4-DAMP, 7.9 for atropine, and 6.2 for pirenzepine, respectively. Thus 4-DAMP has 7.5 times and 440 times greater potency than atropine and pirenzepine to inhibit bethanechol-stimulated secretion. The slope of the Schild regression line was not different from 1. These results suggest that inhibitions of bethanechol-stimulated pancreatic secretion are competitive for 4-DAMP, atropine, and pirenzepine and that bethanechol-stimulated pancreatic secretion is mediated by M3 muscarinic receptors in dogs.

Effects of DN-9693, a synthesized phosphodiesterase inhibitor, on pancreatic exocrine secretion in dogs

The effects of DN-9693, a synthesized phosphodiesterase inhibitor, on the secretion of pancreatic juice were investigated in preparations of the isolated and blood-perfused dog pancreas. DN-9693 injected intraarterially caused a dose-dependent increase in the secretion of pancreatic juice and decrease in the perfusion pressure. The threshold doses to increase the pancreatic secretion and to decrease the perfusion pressure were about 100 micrograms and 1 microgram, to decrease the perfusion pressure were about 100 micrograms and 1 micrograms, respectively. Thus, the secretory response was less effective than the vascular response. The secretory activity of DN-9693 (0.3 mg) was approximately equal to that of 0.03 mg of 3-isobutyl-1-methylxanthine, 0.5 mg of papaverine, 5 mg of theophylline, 0.08 0.5 mg of papaverine, 5 mg of theophylline, 0.08 units of secretin and 0.2 units of cholecystokinin. The concentration of bicarbonate in the pancreatic juice induced by DN-9693 was increased, but protein concentration was not. DN-9693-induced pancreatic secretion was not modified by pretreatments with phentolamine, propranolol, atropine, sulpiride and cimetidine. Secretin-induced pancreatic secretion was significantly potentiated by infusion of DN-9693 (10 micrograms/min), but cholecystokinin-induced one was not. From these results, it is concluded that DN-9693 may produce an increase in pancreatic secretion by acting directly on the pancreatic exocrine gland of the dog, which might be mediated through an increase of intracellular cyclic AMP concentration by inhibiting phosphodiesterase activity.

Collagen-binding affinity of beta-2-microglobulin, a preprotein of hemodialysis-associated amyloidosis

beta 2-Microglobulin (B2M) is the amyloid preprotein that accumulates in amyloid osteoarthropathy associated with hemodialysis. To elucidate the mechanism of such amyloidogenesis, we investigated the interaction between B2M and collagen in vitro by solid-phase enzyme immunoassay. Soluble collagens which had been solidified on plastic plates were allowed to react sequentially with B2M, peroxidase-conjugated antibody to B2M, and the substrate. The collagen-binding activity was dependent on the concentration of B2M and collagen, respectively. These results suggest that the collagen-binding affinity of B2M plays an important role in amyloidogenesis.

Central alpha 2 adrenoceptor-mediated pancreatic exocrine response to yohimbine in anesthetized dog

Effects of yohimbine on the secretion of pancreatic juice in anesthetized dogs were investigated. Intravenous yohimbine (0.1-1 mg/kg) caused dose-dependent increases in the secretion of pancreatic juice and vasodilation. However, intra-arterial yohimbine (0.3-1 mg) did not cause any secretory responses. The secretory activity of 0.3 mg/kg of yohimbine was approximately equal to that of 0.04 U/kg of secretin and 40 mg/kg of 2-deoxy-D-glucose (2-DG). Secretory responses to yohimbine were inhibited by pretreatment with clonidine or atropine and abolished by vagotomy. The concentration of protein in the pancreatic juice induced by yohimbine was increased, but the bicarbonate concentration was scarcely changed. These results indicate that yohimbine stimulates, at least in part, pancreatic exocrine secretion by acting on the central alpha 2 adrenoceptor in the dog.

Effects of nicorandil and verapamil, antianginal agents, on plasma digoxin concentrations in rats and dogs

The effects of equihypotensive doses of nicorandil and verapamil on plasma digoxin concentrations have been assessed in rats and dogs. In a single digoxin dose study, digoxin (1 mg kg-1) alone, or in combination with nicorandil (5 mg kg-1) or verapamil (25 mg kg-1) was given orally to rats. When given chronically to rats, a single dose of digoxin (1 mg kg-1) orally for 7 consecutive days was followed, on day 8, by digoxin alone, or together with nicorandil (5 mg kg-1) or verapamil (25 mg kg-1). In dogs, a loading dose of digoxin (50 micrograms kg-1) was given orally on day 1, then 25 micrograms kg-1 was administered for the following 6 days. On day 8, digoxin (50 micrograms kg-1) was given with nicorandil (5 mg kg-1) or verapamil (20 mg kg-1). In rats, the AUC0-24 and Cmax of plasma digoxin were enhanced significantly by coadministration of verapamil, but not by nicorandil. In dogs, verapamil significantly increased the Cmax of plasma digoxin, but not the AUC. Nicorandil had no effect on either parameter.

Immunological studies on Kawasaki disease: II. Isolation and characterization of an immunosuppressive factor in acute phase sera

Acute phase serum from a patient with Kawasaki disease possessed strong inhibitory activity for the proliferative response of Con A-stimulated peripheral blood mononuclear cells. The inhibitor was fractionated step-wise by means of DEAE-Sephadex A-50 ion exchange chromatography followed by Sephadex G-100 gel filtration and high performance liquid chromatography. A major protein of 140 kD with 2000 times greater inhibitory activity than the original serum was identified in the final fraction. Immunization of mice with this fraction resulted in the production of three hybridoma clones secreting monoclonal antibodies (MoAb) of IgG1 class which blocked the inhibitory activity of the fraction. Two of these MoAb recognized the same epitope of the inhibitory factor, while the remaining MoAb was directed to a different epitope. Western blot analysis of acute phase sera by the MoAb demonstrated the presence of 140 kD molecules in 43 of 55 patients.

Inhibition of lymphocyte DNA synthesis by plasma from patients with Kawasaki disease

Plasma obtained from patients with Kawasaki disease during the acute phase markedly inhibited DNA synthesis in autologous peripheral blood lymphocytes (PBLs) stimulated by phytohaemagglutinin-P (PHA-P) or concanavalin A (Con A). The inhibition became less marked with the progression of the disease and there was no effect on DNA synthesis in PBLs stimulated by pokeweed mitogen (PWM). The plasma also inhibited DNA synthesis in PBLs obtained from healthy adults. The postulated suppressors markedly inhibited DNA synthesis in PBLs from healthy adults stimulated by PHA-P, Con A, purified protein derivative (PPD) or mixed lymphocyte culture reaction (MLR) but they had little effect on the DNA synthesis stimulated by PWM or protein A. With respect to the mechanism, the suppression was found to be potentiated by an increase in the concentration of the patients' plasma, and not to be associated with cytotoxicity nor with a deficiency of factor(s) indispensable for PBL proliferation. It was also evident that the suppression was not related to the concentration of the stimulant, to the lengths of the culturing period nor to the presence of prostaglandins.

Effects of three purine-related compounds on pancreatic exocrine secretion in the dog

The effects of adenosine, adenosine 5'-triphosphate (ATP) and inosine on pancreatic exocrine secretion were investigated in the vascularly isolated and self-haemoperfused dog pancreas. Drugs were injected close-arterially (i.a.) in a single bolus. These three purine-related compounds per se did not affect resting rate of pancreatic secretion and the concentrations of protein and bicarbonate in the resting juice. Graded doses of adenosine (0.1-1.0 mg, i.a.) and ATP (0.1-1.0 mg i.a.) administered 1 min prior to secretin (0.025 clinical units, i.a.) increased a secretin-stimulated secretory volume dose-dependently, and the effects of adenosine and ATP were reversed by pretreatments with theophylline (0.3 mg, i.a.). Inosine (1.0 mg, i.a.) affected neither secretin- nor dopamine-stimulated (3 micrograms, i.a.) pancreatic secretion. Adenosine and ATP did not affect dopamine-stimulated pancreatic secretion. These results suggest that adenosine and ATP (or terminal phosphate hydrolyzed derivatives) enhance secretin-stimulated pancreatic exocrine secretion through 'P1' purine receptors in the exocrine cells, without conversion to inosine.