Construction of squalene-accumulating Saccharomyces cerevisiae mutants by gene disruption through homologous recombination

Saccharomyces cerevisiae synthesizes ergosterol via squalene, but squalene is hardly detected in aerobically grown cells. To obtain a stable squalene-accumulating yeast strain, we attempted to disrupt a gene required in the conversion of squalene to ergosterol, by homologous recombination with a short piece of the gene fragment conjugated with an integration plasmid vector carrying the LEU2 gene. Two mutants that required ergosterol at least for fast growth were isolated. In an aerobic cultivation and with ergosterol supplementation, the two mutants accumulated squalene up to 5 mg/g dry cells. Southern hybridization analysis indicated that both mutants had acquired the vector DNA integrated in the same gene, or nearby genes, on chromosome 12.

Expression of fimbriae and host response in Branhamella catarrhalis respiratory infections

Sputum during the acute exacerbation of chronic respiratory diseases were observed under the electron microscope, to determine the in vivo expression of surface structures of Branhamella catarrhalis (B. catarrhalis), the polymorphonuclear neutrophil (PMN) response to B. catarrhalis infections, and the composition of sputum. It was found that during infection fimbriae are expressed in B. catarrhalis. However, there were sparsely to densely fimbriated bacteria in each sputum sample. The length of the fimbriae were from 50 to 76 nm. In the sparsely fimbriated B. catarrhalis, external to the cell wall, a thin, granular, electron-dense layer was observed. Due to the presence of fimbriae, this layer was not seen in densely fimbriated B. catarrhalis. Blebs were also found in B. catarrhalis. PMNs were found to phagocytose both B. catarrhalis and debris. Evidence was found that debris were formed mainly by the destruction of PMNs. Bacteria as well as debris were phagocytosed by PMNs.

A model system for the continuous production of a heterologous protein using a novel secretion promoting factor which operates in Escherichia coli

The 'PAS factor' whose gene has been cloned from a species of Vibrio, is a novel protein secretion factor which is functional in Escherichia coli cells. To demonstrate that practical use of the PAS factor gene is possible, we have constructed a model secretion vector 'pAS23'. Using this system, beta-lactamase was produced and secreted into the medium of a continuous culture system, after optimization of culture conditions.

Detection of minimal residual disease using clonospecific primers for CDRIII in patients with acute B lymphocytic leukemia with or without Philadelphia chromosome: possibility of clinical application as a tool for improving prognosis

We attempted to identify the minimal residual leukemic clone as related to the clinical course in patients with acute B lymphocytic leukemia (B-ALL). DNA was extracted from stored bone marrow slides, and the third complementarity determining region (CDRIII) was amplified by polymerase chain reaction (PCR) using primers with consensus sequences for VH and JH. After amplification of the CDRIII band, the DNA fragment of CDRIII was inserted into the cloning vector PUC118. After cloning, the DNA sequences for CDRIII were determined. Clonospecific DNA sequences in CDRIII were selected, and clonospecific primers for each patient were synthesized. Using the clonospecific primers, we carried out second-round PCR to detect minimal residual disease (MRD) during several stages of the clinical course. Basically, the sensitivity of detection for MRD was between 10(-4) and 10(-5) cells. Even when leukemic cells were not detected in the morphologic study, with this detection system, the MRD was identified as an amplified CDRIII band stained with ethidium bromide on agarose gel. After bone marrow transplantation (BMT), MRD was detected for at least 4 months. In this article, we discuss the difference in sensitivity of detection for MRD between the BCR-ABL fusion gene and CDRIII in Philadelphia chromosome-positive (Ph+) B-ALL, as well as the possible clinical application of this method to predict relapse and prognosis.

[Reoperation after open mitral commissurotomy for mitral stenosis]

Between 1975 and 1993, 16 of 95 patients who received open mitral commissurotomy for mitral stenosis required reoperation for recurrent mitral lesions with a mean duration of 11 years after the initial operation at Kawasaki Medical School Hospital. The mitral lesions necessitating reoperation involved restenosis in eight, stenoinsufficiency in six and regurgitation in two. In 13 patients, mitral commissure was well separated, and the mitral restenosis and regurgitation were caused by progressions of valvular and subvalvular lesions. Significant tricuspid valve regurgitation was also seen in nine patients, and in seven out of eight patients who were in NYHA functional class III or IV, tricuspid regurgitation of grade 3 was observed. The combined tricuspid regurgitation aggravated the patient's symptoms and became a major risk factor of the reoperation after open mitral commissurotomy.

Dynamic arterial baroreflex in rabbits with heart failure induced by rapid pacing

Excessive sympathetic nerve activity in heart failure could be attributable to impaired arterial baroreflex function. Employing transfer function analysis, we evaluated the arterial baroreflex in control rabbits (n = 8) and in rabbits with rapid pacing-induced heart failure (n = 10) in a dynamic manner. Rabbits in the heart-failure group showed elevated filling pressures, depressed first derivative of left ventricular pressure, pulmonary congestion, and an increased level of plasma norepinephrine. Varying aortic pressure pseudorandomly and recording responses in renal nerve activity, we calculated the transfer function from aortic pressure to renal nerve activity. The gain of the transfer function was similar between control and heart-failure rabbits over 0.04-0.4 Hz as well as the phase and the coherence, indicating that the dynamic arterial baroreflex was preserved in our rabbit heart-failure model. Vagotomy increased the gain of the arterial baroreflex over 0.04-0.4 Hz in control (P < 0.05) but not in heart-failure rabbits, indicating that vagal afferents, which normally inhibit the dynamic arterial baroreflex, no more did so in heart failure. We conclude that excessive sympathetic nerve activity in heart failure may not be due to impaired dynamic arterial baroreflex, but that this apparently preserved arterial baroreflex in heart failure may be due to impaired cardiopulmonary baroreflex.

A novel protein secretion factor from a Vibrio species which operates in Escherichia coli

A DNA fragment specific to a Vibrio species was found to promote extracellular secretion of proteins, when cloned into Escherichia coli. Cells harboring a plasmid carrying this fragment secreted significant amounts of periplasmic beta-lactamase and alkaline phosphatase into the medium, however most cytoplasmic beta-galactosidase was retained within the cell. The DNA sequence essential for this property was found to be a gene encoding 76 amino acids, which was designated as the 'PAS factor'. Highly expressed PAS factor is harmful to the cell, this may be due to a disruption of the membrane structure and/or function.

[A case of hypertrophic obstructive cardiomyopathy (HOCM) complicated by infective endocarditis (IE) and mitral regurgitation (MR)]

The case of a 56-year-old man who underwent mitral valve replacement due to HOCM complicated by IE and MR is reported. Preoperative 2D echocardiographic assessment of the mitral valve revealed systole anterior motion (SAM) and vegetation, and color flow Doppler echocardiographic examination revealed severe mitral regurgitation. The left ventricular out-flow tract gradient decreased from 140 mmHg preoperatively to 60 mmHg postoperatively. Mitral valve replacement should be considered in patients with associated IE and severe MR.

Cloning of a new cryIA(a) gene from Bacillus thuringiensis strain FU-2-7 and analysis of chimaeric CryIA(a) proteins for toxicity

We cloned the cryIA(a) gene from Bacillus thuringiensis strain FU-2-7, one of the toxin genes encoding lepidopteran-specific protoxins. Sequence analysis of the gene showed two amino acid differences (Pro77 to Leu and Phe965 to Ser) from the CryIA(a) of B. thuringiensis strain HD-1. We constructed chimaeric cryIA(a) genes using FU-2-7 and HD-1 cryIA(a) genes and isolated the chimaeric protoxins, as well as the parental ones, from Escherichia coli cells harboring the recombinant plasmids to examine the effects of the two amino acid variations on the toxicity. FU-2-7 CryIA(a) protein was about half as toxic against the smaller tea tortrix, Adoxophyes sp., and one-third as toxic against the silkworm, Bombyx mori, as that of HD-1. On the other hand, a chimaeric CryIA(a) protein with a single replacement of Phe965 to Ser had nearly the same toxicity as the HD-1 CryIA(a) against the smaller tea tortrix and one-third the toxicity against silkworm as that of HD-1. This improved property of the chimaeric CryIA(a) protoxin may be useful for widening its application to crop protection in sericultural countries.

Influence of arotinolol hydrochloride on heart rate spectrum in hypertensive subjects

Influence of arotinolol hydrochloride and atenolol on the balance between the sympathetic and parasympathetic nervous systems was evaluated in 8 hypertensive subjects by spectral analysis of heart rate (HR) and systemic blood pressure (BP). Before and after administration of either arotinolol (n = 7) or atenolol (n = 7) for 2 weeks, BP was continuously and non-invasively monitored by a finger-cuff manometry (Finapres). A time series of instantaneous HR was constructed from the BP signal. A time series of mean BP was also constructed. Spectral analysis was performed by the use of an autoregressive algorithm on these time series (approximately 180 sec). Each spectrum was subdivided into low-(0.05-0.15 Hz, LF) and high-frequency (0.15-0.4 Hz, HF) components, and each component was divided by the sum of the two for normalization. As a measure of the balance between the sympathetic and parasympathetic nervous systems, the ratio of LF to HF (LF/HF) was evaluated. Arotinolol increased fractional HF in the HR spectrum from 0.45 +/- 0.12 to 0.73 +/- 0.08 (p < 0.01) and decreased fractional LF from 0.55 +/- 0.12 to 0.27 +/- 0.08 (p < 0.01); consequently, it decreased LF/HF from 1.4 +/- 0.5 to 0.4 +/- 0.2 (p < 0.01). Atenolol had similar effects on these parameters. Neither of these beta-adrenergic blockades produced a discernible decrease in LF/HF in the BP spectrum. In conclusion, these beta-adrenergic blockades decreased LF/HF in the HR spectrum in hypertensive subjects, which suggests that they improved the balance between the sympathetic and parasympathetic nervous systems.

[Clinical significance of positive blood cultures in the Nagasaki Rosai Hospital during the past 6 years]

In this clinical study we tried to find out the clinical significance of positive blood cultures between Jan. 1984 and Dec. 1989 in the Nagasaki Rosai Hospital. In this period the association between the isolated bacteria from blood cultures (398 specimens: 17.9%) and clinical background were evaluated. Each year the positive cultures were seen in about 18-20%. The distribution of bacteria showed increase percentage of the gram-positive organisms such as coagulase-negative Staphylococcus. Gram-negative organisms in included P. aeruginosa, A. calcoaceticus and E. coli. A. calcoaceticus was frequently found from the dept. of neurosurgery. Fungus, mostly Candida, was isolated in about 10-20%. The specimens were provided from department of internal medicine (62.9%) and neurosurgery (22.8%). An analysis of 213 episodes of 188 bacteremic cases was made. The onset of bacteremia had two peaks, 24 h or 1 month, after admission. The primary infected sites were the urinary tract (26.7%), respiratory system (14.5%) and central nervous system (6.1%). The central venous catheter was an important infected site. The major underlying diseases included acute cerebrovascular diseases, cardiac failure due to valvular heart diseases or acute myocardial infarction and/or iatrogenic immunocompromised state. The major complications were disseminated intravascular coagulation (DIC) (24.4%) and multiple organ failure (MOF) (8.9%). Half of the DIC episodes was caused by gram-positive cocci such as CNS, E. faecalis and MRSA. 68.4% of MOF episodes was associated with gram-negative bacteria. While the remainder was caused by gram-positive cocci including CNS and MRSA.(ABSTRACT TRUNCATED AT 250 WORDS)

Replacement of an amino acid residue of cyclodextrin glucanotransferase of Bacillus ohbensis doubles the production of gamma-cyclodextrin

Cyclodextrin glucanotransferase (CGTase; EC 2.4.1.19) produces cyclodextrin (CD) from starch through an intramolecular transglucosylation reaction. To obtain a better understanding of the amylolytic and cyclization mechanisms of CGTase, and furthermore to improve the production of gamma-CD, mutant CGTases were constructed by site-directed mutagenesis of the CGTase gene of Bacillus ohbensis replacing Tyr at position 188 by 19 other amino acids. All mutant enzymes retained both starch-degrading and CD synthesizing activities to various extents. Among them, a mutant enzyme having Trp instead of Tyr-188 produced 15% of gamma-CD from soluble starch, which is about twice as much as the amount produced by the wild-type enzyme.

Cloning, sequencing, and expression of thermophilic Bacillus sp. strain TB-90 urease gene complex in Escherichia coli

The urease of thermophilic Bacillus sp. strain TB-90 is composed of three subunits with molecular masses of 61, 12, and 11 kDa. By using synthetic oligonucleotide probes based on N-terminal amino acid sequences of each subunit, we cloned a 3.2-kb EcoRI fragment of TB-90 genomic DNA. Moreover, we cloned two other DNA fragments by gene walking starting from this fragment. Finally, we reconstructed in vitro a 6.2-kb DNA fragment which expressed catalytically active urease in Escherichia coli by combining these three DNA fragments. Nucleotide sequencing analysis revealed that the urease gene complex consists of nine genes, which were designed ureA, ureB, ureC, ureE, ureF, ureG, ureD, ureH, and ureI in order of arrangement. The structural genes ureA, ureB, and ureC encode the 11-, 12-, and 61-kDa subunits, respectively. The deduced amino acid sequences of UreD, UreE, UreF, and UreG, the gene products of four accessory genes, are homologous to those of the corresponding Ure proteins of Klebsiella aerogenes. UreD, UreF, and UreG were essential for expression of urease activity in E. coli and are suggested to play important roles in the maturation step of the urease in a co- and/or posttranslational manner. On the other hand, UreH and UreI exhibited no significant similarity to the known accessory proteins of other bacteria. However, UreH showed 23% amino acid identity to the Alcaligenes eutrophus HoxN protein, a high-affinity nickel transporter.

A flavoprotein functional as NADH oxidase from Amphibacillus xylanus Ep01: purification and characterization of the enzyme and structural analysis of its gene

Amphibacillus xylanus Ep01, a facultative anaerobe we recently isolated, shows rapid aerobic growth even though it lacks a respiratory pathway. Thus, the oxidative consumption of NADH, produced during glycolysis and pyruvate oxidation, should be especially important for maintenance of intracellular redox balance in this bacterium. We purified a flavoprotein functional as NADH oxidase from aerobically growing A. xylanus Ep01. The A. xylanus enzyme is a homotetramer composed of a subunit (M(r) 56,000) containing 1 mol of flavin adenine dinucleotide. This enzyme catalyzes the reduction of oxygen to hydrogen peroxide with beta-NADH as the preferred electron donor and exhibits no activity with NADPH. The flavoprotein gene of A. xylanus Ep01 was cloned by using a specific antibody. The amino acid sequence of 509 residues, deduced from the nucleotide sequence, showed 51.2 and 72.5% identities to the amino acid sequences of alkyl hydroperoxide reductase from Salmonella typhimurium and NADH dehydrogenase from alkalophilic Bacillus sp. strain YN-1, respectively. Bacillus spp. have a respiratory chain and grow well under aerobic conditions. In contrast, Amphibacillus spp., having no respiratory chain, grow equally well under both aerobic and anaerobic conditions, which distinguishes these two genera. Salmonella spp., which are gram-negative bacteria, are taxonomically distant from gram-positive bacteria such as Bacillus spp. and Amphibacillus spp. The above findings, however, suggest that the flavoprotein functional as NADH oxidase, the alkyl hydroperoxide reductase, and the NADH dehydrogenase diverged recently, with only small changes leading to their functional differences.

The three-dimensional structure of the colicin E3 immunity protein by distance geometry calculation

The three-dimensional solution structure of the colicin E3 immunity protein (84 residues) was determined by distance geometry calculations. The hydrophilic side of a four-stranded antiparallel beta-sheet constitutes a part of the surface of the protein, and two loops lie on the hydrophobic side of the sheet. All the three specificity-determining residues, which are included in the center of the beta-sheet, display their side groups on the protein surface.

Developmental process: family caregivers of demented Japanese

1. Developmental process of caring for demented elders: the case of family caregivers consists of the beginning process (stage 1 through 4) and the awakening process (stage 5 through 7). 2. In the beginning process, the caregiver is unaware of the interaction between him/her and the demented family member, relies on conventional, general-purpose methods of care and on verbal communication, and consider care in terms of training and discipline of the person cared for. 3. The caregiver in the awakening process has realized that there is interaction between him/her and the demented family member, reflects on the nonverbal signs shown by the elder in order to improve their care, and provide warm and considerate care by making the most of nonverbal communication.

Correlation of orbital muscle changes evaluated by magnetic resonance imaging and thyroid-stimulating antibody in patients with Graves' ophthalmopathy

To evaluate the relationship between eye changes and autoantibody to the thyrotropin receptor in patients with Graves' disease, we evaluated the eye changes using magnetic resonance imaging and the results were correlated with thyroid-stimulating antibody, thyrotropin binding inhibitor immunoglobulin and thyroid growth activity. Subjects were 15 patients with Graves' disease who had Graves' ophthalmopathy, including exophthalmos and other signs and symptoms, and nine patients without ophthalmopathy; all were maintained in a euthyroid state by antithyroid drugs. The thyrotropin-binding inhibitor immunoglobulin was measured by a kit, and thyroid-stimulating antibody and thyroid growth activity were evaluated by cyclic adenosine 3',5'-monophosphate production and [3H]thymidine incorporation, respectively, by cultured functional rat thyroid lined cells. The sum of the swelling ratios (muscle thickness to the diameter of the optic nerve) of the four extraocular muscles correlated well with the degree of exophthalmos. The thyrotropin-binding inhibitor immunoglobulin was positive in nine out of 15 patients with ophthalmopathy; however, no correlation was observed between the activity and exophthalmos or muscle swelling. No significant correlation was observed between muscle changes and thyroid growth activity either. On the other hand, thyroid-stimulating antibody (642 +/- 91%) in Graves' patients with ophthalmopathy was significantly (p < 0.02) higher than that (315 +/- 84%) in patients without ophthalmopathy. Moreover, the level of stimulating activity in Graves' patients with ophthalmopathy showed a significant (p < 0.02) positive correlation with the sum of the swelling ratios of the individual eight eye muscles. These results suggest that thyroid-stimulating antibody has a close relation to Graves' ophthalmopathy.

Mutational analysis of the amino acid residues essential for the cis and trans cleavage activity of the potato virus Y 50-kDa protease

To examine the proteolytic activities of various truncated derivatives of the potato virus Y (PVY) 50-kDa protease, the derivatives were expressed in Escherichia coli in polyprotein forms fused with coat protein (CP). For the intermolecular cleavage reaction, the truncated proteases were expressed together with the substrate protein containing the polymerase-CP junction. The activity was evaluated by the amount of the mature CP released from the precursor by the intra- and intermolecular cleavage occurring in E. coli. By this experiment, we identified the moiety responsible for the proteolytic activity of the 50-kDa protease to be a 26-kDa polypeptide mapped to the C-terminal half of the protease. Introduction of His234-->Tyr, Asp269-->Asn, or Cys339-->Gly substitution in the putative catalytic triad of the protease abolished its activity. However, the mutated protease with Cys339-->Ser replacement retained a reduced proteolytic activity.

Neutrophil response to Pseudomonas aeruginosa in respiratory infection

Sputum from patients with acute exacerbation of respiratory infection by Pseudomonas aeruginosa was observed under the electron microscope. External to the cell wall of P. aeruginosa a granular, electron-dense material was observed which is suggestive of capsule. It is supposed that stabilization of capsule occurred by the host antibody, which was produced due to chronic infection by P. aeruginosa. Mucoid type of microcolonies were observed with a fibrous matrix of exopolysaccharide. Other types of microcolonies were surrounded by granular substances or fine fibers. Neutrophil was found to be partially surrounding the microcolony in an attempt to defense. Debris was formed mainly by the destruction of the neutrophil. Most neutrophils were found full of phagocytosed debris; in contrast only a few neutrophils were found to have phagocytosed P. aeruginosa. This study concludes that instead of phagocytosing bacteria, neutrophil phagocytosed debris and bacteria were not completely eradicated. Therefore, this might be one of the factors in the pathogenesis of respiratory infection and persistent colonization by P. aeruginosa.

Intra-arterial infusion of insulin attenuates vasoreactivity in human forearm

Hyperinsulinemia may contribute to the development of hypertension. The aim of the present study was to determine whether hyperinsulinemia modulates vascular reactivity to phenylephrine or angiotensin II. In 10 young, healthy volunteers, the left brachial artery was cannulated for drug infusion and direct measurements of arterial pressure. We measured forearm blood flow by a strain-gauge plethysmograph while infusing phenylephrine (0.2, 0.8, and 2.4 micrograms/min) and angiotensin II (5, 10, and 20 ng/min) locally into the brachial artery before and during simultaneous intra-arterial infusion of insulin (0.15 mU/kg per minute). Forearm vascular resistance was calculated from directly measured arterial pressure and forearm blood flow. Intra-arterial infusion of insulin raised the local plasma insulin level from 10.3 +/- 1.4 to 133.3 +/- 21.1 microU/mL (P < .01) and did not change blood glucose level in the venous effluents of the forearm. Insulin infusion slightly but not significantly increased basal forearm blood flow (4.6 +/- 1.5 to 5.5 +/- 0.9 mL/min per 100 milliliters, NS) and decreased forearm vascular resistance (22.1 +/- 2.1 to 20.3 +/- 2.8 U, NS). Phenylephrine and angiotensin II increased forearm vascular resistance dose dependently before and during simultaneous insulin infusion (P < .01 for both). Intra-arterial infusion of insulin attenuated vascular reactivity to phenylephrine (P < .01) and angiotensin II (P < .01). None of these drugs changed blood pressure or heart rate. Our results suggest that hyperinsulinemia attenuates vascular reactivity in the forearm resistance vessels in healthy humans.

[Support techniques in the surgical treatment of aneurysms of the aortic arch]

During the last 15 years, we operated 25 patients of aneurysm of the aortic arch. From 1977 to 1990, various support techniques combined with extracorporeal circulation and carotid bypass were used but from 1990 extracorporeal circulation with selective cerebral perfusion was employed, and so postoperative brain damage was decreased from 47% to 10% (p = 0.05) and operative mortality from 53% to 10% (p = 0.03). We now consider that extracorporeal circulation with selective cerebral perfusion is the best method for cerebral protection in the operation of aneurysms of the aortic arch.

[Coronary reoperation--report of 16 cases]

Between January 1975 and July 1992, coronary artery reoperation was performed in 16 of 333 patients who had undergone primary bypass grafting. The interval between the operations ranged from 2 to 147 months. Reoperation was done within one year in two patients, within one to five years in five patients and after more than five years in nine patients. The mean number of bypass grafts was 2.31 per patient in the first operation and 1.75 in the reoperation. The main reasons for the reoperation were an occlusion of the graft in 12 cases and both graft occlusion and new coronary artery disease in 3 cases. In one other case, an emergency right coronary bypass graft done for an acute occlusion during PTCA to an area of right coronary artery stenosis 13 months after two bypass graftings to the LAD and circumflex coronary artery. Fourteen cases had vein graft disease bypassed to the LAD or new coronary artery disease in the LAD and required reoperations of the LAD. In the case with a recurrence of myocardial ischemia after coronary bypass surgery and with bypass grafts to the LAD that were patent, there were no cases requiring reoperation. These findings demonstrate that patency of the grafts to the LAD is an important factor for reoperation after myocardial revascularization surgery.

Different sensitivities of NMDA receptor channel subtypes to non-competitive antagonists

Four kinds of heteromeric N-methyl-D-aspartate (NMDA) receptor channels, the epsilon 1/zeta 1, epsilon 2/zeta 1, epsilon 3/zeta 1 and epsilon 4/zeta 1 channels, were expressed in Xenopus oocytes and their sensitivities to various non-competitive antagonists were examined. The epsilon 1/zeta 1 and epsilon 2/zeta 1 channels were more sensitive to (+)MK-801 (dizocilpine) than the epsilon 3/zeta 1 and epsilon 4/zeta 1 channels, whereas the sensitivities to phencyclidine (PCP), ketamine and N-allylnormetazocine (SKF-10,047) were only slightly variable among the four epsilon/zeta channels. Furthermore, the replacement by glutamine or arginine of the conserved asparagine residue in segment M2 of the epsilon 2 and zeta 1 NMDA receptor channel subunits reduced the sensitivities to PCP, ketamine and SKF-10,047, though to different extents. These results, together with previous findings, suggest that these non-competitive antagonists as well as (+)MK-801 and Mg2+ act on a common site.

Effects of a novel orally effective V1-receptor antagonist, OPC-21268, on AVP-induced sympathoinhibition

Arginine vasopressin (AVP) plays as important role in control of circulation and may be involved in pathophysiology of cardiovascular diseases. Recently a novel oral V1-receptor antagonist, OPC-21268, has been produced for possible human therapeutic use (Y. Yamamure et al. Science Wash. DC 252: 572-574, 1991). OPC-21268 is a nonpeptide antagonist and inhibits AVP-induced vasoconstriction in rats and humans. In this study, we examined the influence of OPC-21268 on the sympathoinhibitory and bradycardic effects of AVP in conscious rabbits. Before OPC-21268, AVP at doses of 1, 3, 10, and 30 mU/kg decreased renal sympathetic nerve activity (RSNA) by 24 +/- 5, 40 +/- 5, 65 +/- 6 and 86 +/- 5%, respectively, and decreased heart rate from 243 +/- 10 beats/min at control to 232 +/- 11, 221 +/- 10, 197 +/- 9, and 166 +/- 6 beats/min, respectively (n = 12). Oral OPC-21268 at 30 mg/kg (n = 12) and 90 mg/kg (n = 5) did not alter the baseline values of arterial pressure, heart rate, and RSNA. After oral OPC-21268 the decreases in RSNA and heart rate evoked with AVP at graded doses were partially but significantly attenuated (P < 0.01). The attenuation of the AVP-induced decreases in RSNA and heart rate was similar between the two doses of OPC-21268. In another group of rabbits (n = 6), intravenous OPC-21268 at 30 mg/kg almost completely abolished AVP-induced decreases in heart rate and RSNA.(ABSTRACT TRUNCATED AT 250 WORDS)