Establishment of the novel B acute lymphoblastic leukemia (FAB L3) cell line KHM-10B with a 13q34 abnormality and constitutive expression of c-myc and max during cell cycle

We established and characterized a new acute lymphoblastic leukemia (ALL-L3 according to FAB classification, or Burkitt's type) cell line, KHM-10B. The morphology of the patient's lymphoblasts and KHM-10B cells corresponded to that of ALL-L3 cells. The cells were positive for HLA-DR, CD19 and surface immunoglobulin (mu, lambda). Southern blot analysis revealed that the fresh lymphoblasts and KHM-10B shared the same immunoglobulin gene rearrangement. Conventional cytogenetic analysis of fresh lymphoblasts from the patient and KHM-10B cells revealed the 13q34 abnormality, the second most common additional abnormality in Burkitt's lymphoma, but no detectable 8q24 involvement. Rearrangement of the c-myc oncogene was not detected by Southern blot analysis. However, a fluorescence in situ hybridization (FISH) assay identified a t(8;22)(q24;q11). The KHM-10B cells were arrested at S phase with hydroxyurea and thymidine, and the synchronized cells progressed through the cell cycle in drug-free medium. The expression of c-myc and max was observed throughout the cell cycle, as was found in the Burkitt's lymphoma cell in Raji. Our findings indicate that FISH analysis is of diagnostic value in detecting obscure chromosomal translocations and that max, as well as c-myc, is expressed constitutively in ALL-L3 and Burkitt's lymphoma cell lines.

Effect of simulated microgravity on auxin polar transport in inflorescence axis of Arabidopsis thaliana

The morphology, growth and development of higher plants are strongly influenced by environmental stimuli on the earth, which affect the changes in the dynamics of plant hormones in plants. Qualitative and quantitative changes in plant hormones are the most important internal factor to regulate plant growth and development. Among them, auxin (IAA) is of most significant. There are numerous reports concerning the physiological roles of auxin in plant growth and development (Matthysse and Scott 1984). One of the characteristics of auxin is to have the ability of polar transport along the vector of gravity on the earth (Schneider and Wightman 1978), suggesting that the activity of auxin polar transport is also important for the growth and development of plants. It has recently been reported that the normal activity of auxin polar transport in inflorescence axis of Arabidopsis thaliana was required for flower formation (Okada et al. 1991, Ueda et al. 1992). Considering the above evidence together with the fact that gravity affects the morphology, growth and development of higher plants, gravity might affect the qualitative and quantitative changes in plant hormones including the activity of auxin polar transport. In this paper, we report the effect of microgravity condition simulated by a three-dimensional (3-D) or a horizontal clinostat on the activity of auxin polar transport in inflorescence axis of Arabidopsis thaliana.

A xanthine derivative denbufylline inhibits negative inotropic response to verapamil in guinea pig ventricular papillary muscles, independent of its phosphodiesterase inhibitory activity

A phosphodiesterase (PDE) III inhibitor, amrinone, inhibited both the negative inotropic actions of verapamil and nicardipine in guinea pig ventricular papillary muscle; this effect was canceled by the protein kinase A inhibitor H-89. The PDE IV inhibitor 1,3-di-n-butyl-7-(2'-oxopropyl)xanthine (denbufylline), which elicited a negative inotropic action by itself, attenuated the action of verapamil up to 10 microM, without any interaction with nicardipine. The attenuation by denbufylline was not influenced by H-89. This suggests that in the ventricular papillary muscle, denbufylline acts on some verapamil-sensitive site(s) in the membrane and interferes with the calcium channel function without involvement of its PDE inhibitory activity.

Bacillus thuringiensis serovar higo (flagellar serotype 44), a new serogroup with a larvicidal activity preferential for the anopheline mosquito

Eight strains of Bacillus thuringiensis, isolated in Japan, formed spherical parasporal inclusions and exhibited low to moderate larvicidal activities for two mosquito species, Anopheles stephensi and Culex pipiens molestus, but not for another dipteran, Telmatoscopus albipunctatus, or two lepidopterans, Bombyx mori and Hyphantria cunea. The anopheline toxicity (LC50 = 6.3 micrograms ml-1) was > 10 times greater than the activity on the Culex mosquito. These strains were assigned to a previously undescribed flagellar (H) antigenic group. On the basis of the representative strain, 92-KU-137-4, a serogroup with H antigen 44, Bacillus thuringiensis serovar higo was established as new.

[Clinical implications of mismatched uptakes of beta-methyl fatty acid analogue and thallium in infarcted myocardium: correlations with coronary stenosis and regional wall motion abnormality]

Myocardial perfusion and fatty acid metabolism were assessed by using myocardial single-photon emission computed tomography with thallium and beta-methyl-p-iodophenyl-pentadecanoic acid (BMIPP) during acute and/or late stages of myocardial infarction in 157 infarcted segments of 100 patients. The incidence of reduced thallium perfusion relative to BMIPP uptake ("T-type" mismatch) was significantly (p < 0.05) lower (9%) compared to that of reduced BMIPP uptake relative to thallium perfusion ("B-type" mismatch) (59%) or non-mismatched segment (32%). In an anteroseptal region, B-type dissociation had a significantly higher incidence compared to no or T-type mismatch; 68% vs. 27% vs. 5%, respectively, whereas the incidence of T-type uptake was relatively high in inferior and posterolateral regions; 13%, 11%, respectively. Severe coronary stenosis was observed in 76% of B-type segments and 72% of non-mismatched segments but in only 43% of T-type segments. The incidence of regional wall motion abnormality was significantly lower (46%) in the T-type mismatch segments when compared to the B-type (91%) or non-mismatched segments (96%). In conclusion, myocardial fatty acid metabolism was more markedly impaired compared to an involved coronary perfusion, resulting in the mismatch of perfusion and fatty acid metabolism. Coronary stenosis and regional wall motion abnormality are more closely related to "B-type" mismatch but not necessarily to "T-type" dissociation, probably because of attenuation artifacts in inferior and posterolateral regions in thallium scan.

Effects of gomisin A on the promotor action and serum bile acid concentration in hepatocarcinogenesis induced by 3'-methyl-4-dimethylamino-azobenzene

The effects of gomisin A, a lignan component of Schizandra fruits, on the promotion stage of hepatocarcinogenesis initiated by 3'-methyl-4-dimethylamino-azobenzene (3'-MeDAB) in male Donryu rats were investigated. When different types of tumor promotors, phenobarbital (PB) and deoxycholic acid (DCA), were administered for 5 weeks after initiation by 3'-MeDAB, preneoplastic alterations in the liver, determined by glutathione S-transferase placental form (GST-P), were markedly increased. Gomisin A significantly inhibited the increase in number and size of GST-P positive foci, regardless of the promotor. This lignan inhibited the increase in serum bile acid concentration by administration of DCA, but hardly influenced the serum bile acids in the PB-combined group. These results suggest that the inhibitory effect of gomisin A on the promotive action of DCA is based on improving bile acid metabolism, but regarding the action of PB, the effect could not be elucidated from the metabolism of bile acids.

Structure-activity relationships of alkylxanthines: alkyl chain elongation at the N1- or N7-position decreases cardiotonic activity in the isolated guinea pig heart

Relationships between the alkyl substitutions (C1-C6) and cardiac inotropic activities of xanthine derivatives were studied in isolated guinea pig heart muscles. Most of the alkylxanthines exhibited positive inotropic activity on the left atrium, which was increased with an elongation of alkyl chain at the N3-position but decreased by substitution of a long alkyl group at the N1- or N7-position of the xanthine skeleton. Although positive inotropic activity in the right ventricular papillary muscle was also increased by longer alkyl groups at the N3-position, the inotropic activity became negative with an increment in alkyl chain length at the N1- or N7-position. The positive inotropic activity of alkylxanthines was correlated with their inhibitory activity on the phosphodiesterase (PDE) III isoenzyme. Adenosine A1 antagonism and PDE IV inhibitory activity were also partly associated with the inotropic activity because H-89, an inhibitor of cyclic AMP-dependent protein kinase, diminished the positive inotropic action and potentiated the negative inotropic action. These results indicate that the positive inotropic activity of alkylxanthines becomes weak with elongation of alkyl chains at the N1- and N7-positions; In particular, xanthines having two long alkyl chains show a negative inotropic activity on the right ventricular papillary muscle, an effect that could not be elucidated from their cyclic AMP-dependent action.

Reversal of drug sensitivity in MDR subline of P388 leukemia by gene-targeted antisense oligonucleotide

We attempted to reverse multidrug resistance (MDR) by treatment with 25-mer antisense phosphorothioate oligonucleotide. The phosphorothioate analogs, the sequences of which are sense or antisense to the initiation codon of mouse mdr1 mRNA, were tested against murine leukemic P388/S and adriamycin-resistant P388/ADR cell lines. A weak inhibitory effect on the growth of P388/S and P388/ADR cells was observed at a sense and antisense oligonucleotide concentration of 30 microM. Using the monoclonal antibody to P-glycoprotein and a flow cytometry technique, we showed that the level of expression of P-glycoprotein in P388/ADR cells treated with antisense oligonucleotide was lower than when treated with sense oligonucleotide. The antisense oligonucleotide potentiated the growth-inhibitory effect of vinblastine on P388/ADR cells, whereas sense oligonucleotide did not. This was accompanied by an increase in vinblastine retention in the cells. The reversal of the resistance by antisense oligonucleotide was increased by the combination with 1 microM verapamil. These results suggest that the antisense oligonucleotide and low dose verapamil may be useful in circumventing the resistance to anticancer drugs of MDR tumors.

Interaction between activin A and cAMP in the induction of FSH receptor in cultured rat granulosa cells

The acquisition of FSH receptor during preantral folliculogenesis is believed to be a key step in the subsequent development of follicles. We examined the interaction between activin and cAMP in FSH receptor induction in rat granulosa cells by measuring 125I-FSH binding and FSH receptor mRNA. In the 125I-FSH binding study, 0.2 mM 8-Br-cAMP and 1 microM forskolin were maximally effective in FSH receptor induction (169 and 220% respectively of control), while higher concentrations gave attenuated responses. It appears that cAMP has ambivalent effects on FSH receptor induction depending on the concentration and length of exposure. Activin alone dramatically increased the number of FSH receptors (314% of control). Moreover, synergistic effects of activin and 8-Br-cAMP or forskolin were observed on FSH receptor induction: a combination of activin (80 ng/ml) and low doses of 8-Br-cAMP (0.2 mM) or forskolin (1 microM) was most effective (160 or 140% of that induced by activin alone) and receptor levels reached a maximum at 24 h. These levels than markedly decreased after 72 h of incubation. Northern blot analysis revealed that the combination of activin (80 ng/ml) and 8-Br-cAMP (0.2 mM) or forskolin (1 microM) increased FSH receptor mRNA to about 140% of that induced by activin alone. These results indicate that activin and cAMP induced FSH receptor synergistically. However, activin did not enhance the production of cAMP induced by forskolin. In addition, a protein kinase A inhibitor (H89) (2 microM), which inhibited the effects of forskolin, had no effect on the action of activin.(ABSTRACT TRUNCATED AT 250 WORDS)

Mutations of the basic amino acid transporter gene associated with cystinuria

To investigate the function of a basic and neutral amino acid transporter-like protein (rBAT) which is a candidate gene for cystinuria, we analysed the rBAT gene in cystinuric patients. Patient 1 is a compound heterozygote with mutations in the rBAT gene causing a glutamine-to-lysine transition at amino acid 268, and a threonine-to-alanine transition at amino acid 341, who inherited these alleles from his mother (E268K) and father (T341A), respectively. Injection of T341A and E268K mutant cRNAs into oocytes decreased transport activity to 53.9% and 62.5% of control (L-cystine transport activity in oocytes injected with wild-type rBAT cRNA), respectively. Co-injection of E268K and T341A into oocytes strongly decreased amino acid transport activity to 28% of control. On the other hand, co-injection of wild-type and mutant rBAT did not decrease transport activity. Furthermore, immunological studies have demonstrated that the reduction of amino acid transport is not due to a decrease in the amount of rBAT protein expressed in oocyte membranes. These results indicate that mutations in the rBAT gene are crucial disease-causing lesions in cystinuria. In addition, co-injection experiments suggest that rBAT may function as a transport activator or regulatory subunit by homo- or hetero-multimer complex formation.

Gender effect on prognosis of patients receiving long-term home oxygen therapy. The Respiratory Failure Research Group in Japan

Although long-term home oxygen therapy (LTOT) certainly prolongs survival, it is not known whether this advantageous effect is similar for both sexes. In this study, we analyzed sex-related differences in survival based on a very large population that had received LTOT from 1986 to 1993. A total of 9,759 patients with chronic obstructive pulmonary disease (COPD), sequelae of tuberculosis (TBsq), and chronic interstitial pneumonia (IP) were selected in 1,212 medical institutions for analysis of survival rates. The survival rates of both sexes were compared with each other using the Cutler-Ederer Method. Despite higher PaCO2 at the beginning, the survival rate of women was significantly better than that of men in these three disease categories. Cox's proportional hazards analysis further confirmed the gender effect on survival by eliminating the effects of age, PaO2, PaCO2, %VC, and FEV1/FVC. The mean survival periods of the women who died during follow-up periods were also significantly longer than those of men (0.41 yr in COPD, 1.84 yr in TBsq, and 0.78 yr in IP). From these findings, we conclude women have a better prognosis than men when they start receiving LTOT, regardless of the cause of respiratory failure.

[Effects of inhaled oxitropium bromide, an anticholinergic drug, on pulmonary hemodynamics in patients with chronic obstructive pulmonary diseases]

We studied the effects of the inhaled anticholinergic agent oxitropium bromide (Ox) on pulmonary hemodynamics in eleven patients with chronic obstructive pulmonary disease. All the patients underwent right heart catheterization and seven of them underwent an incremental ergometer exercise test while in the supine position. Pulmonary hemodynamics and arterial blood gases were measured at rest and during maximal exercise, before and 30 minutes after inhalation of 2 puffs (200 micrograms) of Ox. Inhalation of Ox did not significantly change pulmonary hemodynamics at rest. The mean pulmonary arterial pressure and the mean pulmonary capillary wedge pressure during exercise decreased significantly (from 40.3 +/- 4.6 to 37.7 +/- 3.9 mmHg, and from 20.4 +/- 3.5 to 17.1 +/- 2.7 mmHg, respectively, mean +/- SE). However, neither cardiac output nor pulmonary vascular resistance changed with inhalation of the drug, at rest or during exercise. We therefore conclude that this commonly used dose of Ox does not directly affect the pulmonary vascular system. The small but significant decreases in pulmonary arterial pressure and pulmonary capillary wedge pressure with Ox may have been indirect effects, caused by bronchodilation.

Use of local cerebral blood flow monitoring to predict brain damage after disturbance to the venous circulation: cortical vein occlusion model by photochemical dye

A rat model of cortical vein occlusion by the photochemical thrombotic technique was used to evaluate whether monitoring the change in the local cerebral blood flow (LCBF) could predict brain damage after cortical vein occlusion. The cortical vein occlusion was attained by using the photochemical thrombotic technique, and the sequential LCBF was measured by using a laser Doppler flowmeter positioned over the middle frontal cortex between two adjacent dorsal veins for 120 minutes after the start of the irradiation to the cortical vein. Rats were assigned to one of three experimental groups. In Group A (n = 10), one dorsal cerebral vein was occluded; in Group B (n = 10), two adjacent dorsal cerebral veins were occluded; and in a sham-operated group (n = 5), the rats also underwent craniotomy and light exposure but received injections of saline rather than the rose bengal dye. After 24 hours, the rats were submitted to perfusion fixation and were examined histopathologically. After irradiation-induced cortical vein occlusion, a gradual and significant decrease of the LCBF was observed in both Group A (significantly different from the LCBF of the sham-operated group after 90 min, P < 0.05, and 120 min, P < 0.01) and Group B (significantly different from the LCBF of the sham-operated group at 30 min, P < 0.05, and at 60, 90, and 120 min, P < 0.01). Significant differences (P < 0.01) in the LCBF were also seen between the two experimental groups at 90 and 120 minutes after the start of the irradiation and the subsequent brain damage.(ABSTRACT TRUNCATED AT 250 WORDS)

[A case of bilateral partial anomalous pulmonary venous connections with the right upper pulmonary vein draining to the high superior vena cava]

A 10-year-old girl with bilateral partial anomalous pulmonary venous connections (PAPVC) was referred to us. The right upper pulmonary vein (PV) drained to the high superior vena cava (SVC) and the left upper PV to the left innominate vein. The left upper PV was directly anastomosed to the right atrial appendage. The SVC was divided distal to the orifice of the right upper PV and anastomosed to the right atrial appendage. A Xenomedica patch was placed within the right atrium to divert the pulmonary venous blood from the SVC orifice across the surgically enlarged ASD to the left atrium. The postoperative course was satisfactory without arrhythmia, and cineangiography revealed no obstruction at the SVC and the right upper PV pathways. We thought that this method is advantageous in preserving the sinus node and its feeding artery, as well as being applicable to the PAPVC to the high SVC.

Effects of platelet depletion on PMA-induced acute lung injury in awake sheep

Little is known about the role of circulating platelets in PMA-induced lung injury in vivo. We investigated the effects of platelet depletion (PD) on the injury using seven unanesthetized sheep with lung lymph fistulas and eight other sheep for morphological study. PD diminished a decrease in the lymph to plasma concentration ratio (L/P) after 1 microgram/kg PMA treatment (n = 4) and caused more increases in lung lymph flow, L/P and lung lymph clearance after 5 micrograms/kg PMA treatment (n = 3) than in control sheep. The high dose was lethal to platelet-depleted sheep. However, PD had no effects on pulmonary hemodynamics. Morphologically, alveolar hemorrhages and exudate, and bleb formation of type I epithelial cells were more prominent in the platelet-depleted sheep than in the control sheep. We conclude that circulating platelets have protective effects against PMA-induced lung injury but have little involvement in PMA-induced pulmonary hypertension.

Importance of prevention of intravenous thrombosis and preservation of the venous collateral flow in bridging vein injury during surgery: an experimental study

BACKGROUND

Venous infarction (cerebral edema and/or hemorrhage) may occur several hours after sacrifice of the bridging vein during surgery. However, in our experience, severe venous infarction is often produced by prolonged brain retraction in addition to sacrifice of the vein.

METHODS

The experiment was carried out using 20 adult cats. In five cats, all bridging veins were coagulated near the superior sagittal sinus and 12 hours later the surgical wound was closed (group A). In five other cats, a round plate weighing 45 g was placed on the center of the Sylvian fissure for 12 hours and then the wound was closed (group B). In the remaining 10 cats, both of these interventions were performed (group C). All 20 animals were sacrificed 12 hours after the wound closure.

RESULTS

The degree of Evans-blue dye leakage and brain edema was much more marked in the group C than in groups A and B. The endothelial intactness of the bridging veins studied by staining with a factor VIII-related antigen was much more disturbed in group C than in the other groups.

CONCLUSIONS

The endothelium of the cortical veins is damaged much more by the combination of sacrifice of the vein and brain retraction, and this endothelial damage of the cortical vein leads to extensive venous infarction.

Identification of the Tax interaction region of serum response factor that mediates the aberrant induction of immediate early genes through CArG boxes by HTLV-I Tax

Tax of human T-cell leukemia virus type I (HTLV-I) activates transcription at a CArG box of various immediate early genes such as the proto-oncogene c-fos. To do this, Tax does not directly bind to the CArG box, but instead binds to the CArG binding factor SRF. In this study, we investigated the domain of SRF required for the activation by Tax and studied the role of this domain on transcriptional regulation at the CArG box. Using a fusion protein of SRF with a yeast transcription factor GAL4, the 14 amino acid (aa) portion (aa 422-435) of SRF was identified as the domain required for Tax activation [Tax-responsive region of SRF (TRRS)]. By means of a two hybrid system, we showed that TRRS was essential for the interaction of SRF with Tax in vivo. The over-expression of SRF with a deletion of TRRS inhibited the Tax activation at the CArG box. Thus, TRRS is the domain of SRF that is essential for Tax activation at the CArG box. Unlike to Tax activation, TRRS was not required for TPA (12-o-tetradecanoylphobol-13-acetate) induction at the CArG box, but a TRRS deletion enhanced the basal activity at the CArG box both under serum-starved and TPA-stimulated conditions. These results suggest that TRRS negatively regulates the transcriptional activation function of SRF, and consequently contributes to the low basal activity at the CArG box before TPA induction.

Immunoelectron microscopic study of HTLV-II-producing cells with an anti-envelope gp46 monoclonal antibody

We observed expression of envelope gp46 protein on an HTLV-II-producing T-cell line (Mo) cells by an immunoelectron microscopical method using a monoclonal antibody against HTLV-II gp46. gp46 reactivity was observed on virus-like particles, extracellular vesicles, cell membrane, and partially in nuclear membrane and endoplasmic reticulum.

Activation of ornithine decarboxylase in epithelial cells of rat intestine

Intestinal ornithine decarboxylase (ODC) is strongly induced by dietary amino acid and protein feeding. However, the consequence of this induction is unknown. In this study, we analyzed the relationship between intestinal ODC activity and DNA synthesis in villus and crypt cells of rat intestine. Single amino acid diets and protein diets stimulated ODC activity in villus cells, but not in crypt cells. However a 20% casein diet induced ODC activity and increased the putrescine concentration in villus and crypt cells. Administration of alpha-difluoromethylornithine, a suicide inhibitor of ODC, prevented both an increase in putrescine level and DNA synthesis in the crypt cells. Observations suggested that the induction of ODC is necessary to initiate DNA synthesis in rat intestinal epithelium.

Chromosome assignments of genes for human Na(+)-dependent phosphate co-transporters NaPi-3 and NPT-1

Chromosome assignments for the genes encoding human renal high affinity Na/phosphate co-transporters NaPi-3 and NPT-1 were derived by analyzing somatic cell hybrid DNAs. Polymerase chain reaction (PCR), using primers specific for two human Na/Pi co-transporters demonstrated that the genes for NaPi-3 was assigned to human chromosome 5 while that for NPT-1 was assigned to human chromosome 6. Renal phosphate transporter genes may be candidates for causing hereditary hypophosphatemia with hypercalciuria in humans.

Production of functional chick liver HMG 2a protein in Escherichia coli

An efficient Escherichia coli system for the production of a variant form of high-mobility group-2a protein (HMG 2a), having the additional 5 amino acid residues (Ala-Pro-Thr-Leu-Glu) at the NH2-terminal, has been constructed. cDNA encoding HMG 2a was ligated with the Omp A signal peptide sequence and was inserted into an inducible bacterial expression vector pSH-L. After the plasmid introduced into E. coli was expressed by temperature shift, the recombinant product was purified by trichloacetic acid precipitation followed by Bio-Rex 70 column chromatography. The purified product showed the expected NH2-terminal sequence and the superhelical activity of circular DNA similar to the authentic HMG 2a isolated from chick liver.

Serum antibody against Helicobacter pylori assayed by a new capture ELISA

We developed a highly specific detection technique for serum antibody, using a monoclonal antibody to a specific antigen of Helicobacter pylori. A monoclonal antibody preparation that reacted with the 54-kDa molecule of H. pylori antigens was obtained. Using this preparation, an antigen-capture enzyme-linked immunosorbent assay (ELISA) was established by fixation of the monoclonal antibody, followed by reaction with sonicated whole cell antigens. The serum antibody titers of patients with gastritis and peptic ulcers were significantly higher than control titers, and the antibody titer correlated with the histological severity of gastritis. Patients positive for H. pylori by bacterial culture had higher titers than H. pylori-negative patients. Our new ELISA may be useful for the diagnosis of H. pylori infections and for evaluation of the severity of gastric inflammation.

Purification and characterization of beta-N-acetylglucosaminidase from Alteromonas sp. strain O-7

beta-N-Acetylglucosaminidase (EC 3.2.1.30) was purified from the outer membrane of a marine bacterium, Alteromonas sp. strain O-7. The enzyme (GlcNAcase A) was purified by successive column chromatographies. The purified enzyme was found to be homogeneous on sodium dodecyl sulfate polyacrylamide gel electrophoresis. The molecular mass and pI of GlcNAcase A were 92kDa and 4.9, respectively. The optimum pH and temperature were 6.0-7.0 and 45 degrees C, respectively. GlcNAcase A was stable up to 40 degrees C at pH 7.0, and hydrolyzed N-acetylchitooligosaccharides from dimer to hexamer. The amino-terminal 16 amino acid residues of GlcNAcase A were sequenced.

Dependency on the rate of change in PaO2 of the ventilatory response to progressive hypoxia

The biphasic nature of the ventilatory response to sustained hypoxia (< 1 h) is thought to occur as a result of combined effects of stimulation and depression with hypoxia. If the depressant effect of hypoxia on ventilation occurs later than the stimulatory effect, the magnitude of the ventilatory response to progressive hypoxia may be different according to the time required for a given fall in PaO2 during the test. In this study, we measured, in 10 healthy adult volunteers, ventilatory responses to isocapnic progressive hypoxia (HVR) using three different protocols (4 min, 6 min, and 15 min for SaO2 to decrease from the baseline to 80%) with or without pretreatment using theophylline (300 mg twice a day), an adenosine receptor antagonist, in a 2-d, single-blind crossover design. The slope values of HVR with the placebo were 0.31 +/- 0.04 (SE) (L/min/% fall of SaO2) in the 4-min protocol, 0.26 +/- 0.04 in the 6-min protocol, and 0.18 +/- 0.04 in the 15-min protocol. The HVR for the 15-min protocol was significantly lower than that for the 4-min or 6-min protocol. The HVR with theophylline was 0.46 +/- 0.08 for the 4-min protocol, 0.54 +/- 0.09 for the 6-min protocol, and 0.66 +/- 0.11 for the 15-min protocol, among which there were no significant differences. The dependency of HVR on the rate of change in PaO2, that was seen with a placebo run, disappeared after pretreatment with theophylline.(ABSTRACT TRUNCATED AT 250 WORDS)