Surface electromyographic evaluation of the neuromuscular activation of the inspiratory muscles during progressively increased inspiratory flow under inspiratory-resistive loading.

This study aimed to evaluate neuromuscular activation in the scalene and sternocleidomastoid muscles using surface electromyography (EMG) during progressively increased inspiratory flow, produced by increasing the respiratory rate under inspiratory-resistive loading using a mask ventilator. Moreover, we attempted to identify the EMG inflection point (EMGIP) on the graph, at which the root mean square (RMS) of the EMG signal values of the inspiratory muscles against the inspiratory flow velocity acceleration abruptly increases, similarly to the EMG anaerobic threshold (EMGAT) reported during incremental-resistive loading in other skeletal muscles. We measured neuromuscular activation of healthy male subjects and found that the inspiratory flow velocity increased by approximately 1.6-fold. We successfully observed an increase in RMS that corresponded to inspiratory flow acceleration with ρ ≥ 0.7 (Spearman's rank correlation) in 17 of 27 subjects who completed the experimental protocol. To identify EMGIP, we analyzed the fitting to either a straight or non-straight line related to the increasing inspiratory flow and RMS using piecewise linear spline functions. As a result, EMGIP was identified in the scalene and sternocleidomastoid muscles of 17 subjects. We believe that the identification of EMGIP in this study infers the existence of EMGAT in inspiratory muscles. Application of surface EMG, followed by identification of EMGIP, for evaluating the neuromuscular activation of respiratory muscles may be allowed to estimate the signs of the respiratory failure, including labored respiration, objectively and non-invasively accompanied using accessory muscles in clinical respiratory care.

Activated ROCK II by-passes the requirement of the CDK2 activity for centrosome duplication and amplification.

Initiation of centrosome duplication and DNA replication is coupled, which is primarily achieved by the late G1 phase-specific activation of cyclin-dependent kinase 2 (CDK2)-cyclin E, which triggers both centrosome duplication and DNA replication. Uncoupling of these two events contributes to overduplication of centrosomes, resulting in the presence of more than two centrosomes (centrosome amplification). Centrosome amplification, which is frequently observed in cancers, contributes to tumor development through destabilizing genomes. Nucleophosmin (NPM/B23) is one of the phosphorylation targets of CDK2-cyclin E for the initiation of centrosome duplication. It has been found that NPM/B23 phosphorylated on Thr199 by CDK2-cyclin E acquires a high binding affinity to ROCK II kinase. The Thr199-phosphorylated NPM/B23 physically interacts with and super-activates the centrosomally localized ROCK II, which is a critical event for centrosomes to initiate duplication. Here, we provide direct evidence for the activation of ROCK II as a primary and sufficient downstream event of CDK2-cyclin E for the initiation of centrosome duplication and for the induction of centrosome amplification.

Roles of cyclins A and E in induction of centrosome amplification in p53-compromised cells.

Abnormal amplification of centrosomes, which occurs frequently in cancers, leads to high frequencies of mitotic defect and chromosome segregation error, profoundly affecting the rate of tumor progression. Centrosome amplification results primarily from overduplication of centrosomes, and p53 is involved in the regulation of centrosome duplication partly through controlling the activity of cyclin-dependent kinase (CDK) 2-cyclin E, a kinase complex critical for the initiation of centrosome duplication. Thus, loss or mutational inactivation of p53 leads to an increased frequency of centrosome amplification. Moreover, the status of cyclin E greatly influences the frequency of centrosome amplification in cells lacking functional p53. Here, we dissected the roles of CDK2-associating cyclins, namely cyclins E and A, in centrosome amplification in the p53-negative cells. We found that loss of cyclin E was readily compensated by cyclin A for triggering the initiation of centrosome duplication, and thus the centrosome duplication kinetics was not significantly altered in cyclin E-deficient cells. It has been shown that cells lacking functional p53, when arrested in either early S-phase or late G(2) phase, continue to reduplicate centrosomes, resulting in centrosome amplification. In cells arrested in early S phase, cyclin E, but not cyclin A, is important in centrosome amplification, whereas in the absence of cyclin E, cyclin A is important for centrosome amplification. In late G(2)-arrested cells, cyclin A is important in centrosome amplification irrespective of the cyclin E status. These findings advance our understandings of the mechanisms underlying the numeral abnormality of centrosomes and consequential genomic instability associated with loss of p53 function and aberrant expression of cyclins E and A in cancer cells.

The effect of rebamipide on Helicobacter pylori extract-mediated changes of gene expression in gastric epithelial cells.

BACKGROUND: Recent studies have shown that Helicobacter pylori affects intracellular signal transduction in host cells, leading to the activation of transcriptional factors and the induction of pro-inflammatory cytokines. On the other hand, rebamipide, an anti-gastritis and anti-ulcer agent, could scavenge reactive oxygen species and reduce interleukin-8 (IL-8) expression in gastric epithelial cells induced by H. pylori-stimulation through the attenuated activation of nuclear factor-kappaB (NF-kappaB). AIMS: In this study, we investigated the effects of rebamipide on gene expression in H. pylori-stimulated epithelial cells using DNA chip. METHODS: H. pylori water extract (HPE) was prepared from NCTC11637, the type strain of H. pylori. Total RNA was extracted from MKN45 cells, a human gastric cancer cell line, following HPE-stimulation with and without rebamipide for 3 h, and differences in gene expression profiles were observed using GeneChip and Human 6800 probe array. RESULTS: The GeneChip analysis demonstrated that 132 up-regulated genes and 873 down-regulated genes, such as growth factors, chemokines and transcription factors, were detected in MKN45 cells 3 h after stimulation of H. pylori. Among them, several genes, including bFGF, RANTES and MIP-2beta, were previously unknown to be expressed in H. pylori-stimulated human gastric cells. Rebamipide reduced expression of 119 genes encoding cytokines, growth factors and their receptors and transcription factors. CONCLUSIONS: These findings suggest that rebamipide could inhibit inflammatory reactions and tumour progression by modifying H. pylori infection-induced gene expression in gastric epithelial cells.

Analysis of IgE turnover in non-sensitized and sensitized rats.

BACKGROUND: Although the levels of immunoglobulin E (IgE) in the circulating blood are often elevated in patients with allergic diseases, such levels cannot always be considered as pathognomonic signs of allergy. The induction of allergic reactions in the tissue was inferred to be related to the amount of IgE passing through the vascular wall. AIMS: We attempted to clarify which compartment, the intravascular or extravascular, plays an important role in the regulation of the turnover of rat IgE. METHODS: The level of DNP-specific rat IgE in the serum was estimated by IgE-capture enzyme-linked immunosorbent assay, and the turnover of IgE was analyzed from its pharmacokinetic parameters. RESULTS: The transfer rate constants from the central to tissue compartment (Kct) were larger than those from the tissue to central compartment (Ktc) irrespective of the sensitized state. The value of the distribution volume of the tissue compartment (Vt) was larger than that of the distribution volume of the central compartment (Vc) irrespective of the sensitized state. CONCLUSIONS: These Findings suggest that the short half-life of rat IgE in the circulation could be attributable to the distribution of IgE from the intravascular to the extravascular compartment.

Outbreak of influenza type A (H1N1) in Iporanga, São Paulo State, Brazil.

From June to July 1999 an outbreak of acute respiratory illness occurred in the town of Iporanga. Out of a total of 4,837 inhabitants, 324 cases were notified to the Regional Surveillance Service. Influenza virus was isolated from 57.1% of the collected samples and 100% seroconversion to influenza A (H1N1) was obtained in 20 paired sera tested. The isolates were related to the A/Bayern/07/95 strain (H1N1). The percentages of cases notified during the outbreak were 28.4%, 29.0%, 20.7%, 6.2% and 15.7% in the age groups of 0-4, 5-9, 10-14, 15-19 and older than 20 years, respectively. The highest proportion of positives was observed among children younger than 14 years and no cases were notified in people older than 65 years, none of whom had been recently vaccinated against influenza. These findings suggest a significant vaccine protection against A/Bayern/7/95, the H1 component included in the 1997-98 influenza vaccine for elderly people. This viral strain is antigenically and genetically related to A/Beijing/262/95, the H1 component of the 1999 vaccine. Vaccines containing A/Beijing/262/95 (H1N1) stimulated post-immunization hemagglutination inhibition antibodies equivalent in frequency and titre to both A/Beijing/262/95-like and A/Bayern/7/95-like viruses. Thus, this investigation demonstrates the effectiveness of vaccination against influenza virus in the elderly.

The nucleotide sequence of dinitrophenyl-specific IgE and Fc(epsilon)RI alpha-subunit obtained from FE-3 hybridoma cells.

FE-3 cells were established by Hanashiro et al. by hybridizing mouse myeloma cells (Sp2/0-Ag14/SF) with rat spleen cells that were freshly isolated from Brown-Norway rats sensitized with DNP-As. FE-3 cells can constitutively secrete IgE without stimulation by cytokines. Our preliminary experiments demonstrated that the IgE secretion was decreased at 3 days after start of culture and the addition of exogenous IgE into culture media depressed the secretion of IgE. Thus, we hypothesized that the IgE production in FE-3 cells may be regulated by a signal transduction through the binding of IgE to its high affinity receptor (Fc(epsilon)RI) or to an IgE binding protein on the cell surface. In this study, we aimed to identify the nucleotide sequence of IgE FE-3 and compared with those of mouse IgE and IgE IR162 to find a structural heterogeneity in the Fc region of IgE FE-3. We also tested if the mRNA of Fc(epsilon)RI was expressed in FE-3 cells using the reverse transcriptase-polymerase chain reaction (RT-PCR) method with the combination of sequencing analysis. Consequently, the cDNA sequence of IgE FE-3 was identical to that of the CH3 and CH4 domains in the epsilon-chain of rat IgE IR162, whereas the cDNA of Fc(epsilon)RI was identical to that of mouse, suggesting that the genes of IgE FE-3 and Fc(epsilon)RI was derived from that of rat spleen cells and mouse myeloma cells, respectively.

Habutobin recognizes Thr(7) in the sequence of fibrinopeptide A of rabbit fibrinogen.

Habutobin, a thrombin-like enzyme from Trimeresurus flavoviridis venom, cleaves only the Arg(16)-Gly(17) bond in the rabbit Aalpha chain and releases fibrinopeptide A (FPA). To investigate the role of amino acid residues in the rabbit FPA sequence upon habutobin action, we examined the inhibitory effects of FPA and peptides containing partial sequences of FPA on the habutobin action. Fibrinopeptides from rabbit, human, bovine and dog were isolated and rabbit FPA was fragmented using dilute HCl. Rabbit FPA inhibited the action of habutobin although FPA from human, bovine and dog did not. Among the fragments of rabbit FPA, a heptapeptide Aalpha 3-9, the N-terminal region of rabbit FPA, competitively inhibited the release of FPA by habutobin, whereas the C-terminal hexapeptide of FPA (Aalpha 11-16) exerted no effect on the habutobin action. Synthetic tripeptides Ser-Thr-Phe corresponding to Aalpha 6-8 and Ala-Thr-Phe also inhibited the habutobin action, but Ser-Asp-Phe and Ala-Thr-Gly did not. It is concluded that habutobin would recognize the region around Thr(7)-Phe(8) in the sequence of rabbit FPA (Aalpha 1-16) prior to the cleavage of the Arg(16)-Gly(17) bond.

Cloning of a Sphingomonas paucimobilis SYK-6 gene encoding a novel oxygenase that cleaves lignin-related biphenyl and characterization of the enzyme.

Sphingomonas paucimobilis SYK-6 transforms 2,2'-dihydroxy-3,3'-dimethoxy-5,5'-dicarboxybiphenyl (DDVA), a lignin-related biphenyl compound, to 5-carboxyvanillic acid via 2,2',3-trihydroxy-3'-methoxy-5,5'-dicarboxybiphenyl (OH-DDVA) as an intermediate (15). The ring fission of OH-DDVA is an essential step in the DDVA degradative pathway. A 15-kb EcoRI fragment isolated from the cosmid library complemented the growth deficiency of a mutant on OH-DDVA. Subcloning and deletion analysis showed that a 1.4-kb DNA fragment included the gene responsible for the ring fission of OH-DDVA. An open reading frame encoding 334 amino acids was identified and designated ligZ. The deduced amino acid sequence of LigZ had 18 to 21% identity with the class III extradiol dioxygenase family, including the beta subunit (LigB) of protocatechuate 4,5-dioxygenase of SYK-6 (Y. Noda, S. Nishikawa, K.-I. Shiozuka, H. Kadokura, H. Nakajima, K. Yano, Y. Katayama, N. Morohoshi, T. Haraguchi, and M. Yamasaki, J. Bacteriol. 172:2704-2709, 1990), catechol 2,3-dioxygenase I (MpcI) of Alcaligenes eutrophus JMP222 (M. Kabisch and P. Fortnagel, Nucleic Acids Res. 18:3405-3406, 1990), the catalytic subunit of the meta-cleavage enzyme (CarBb) for 2'-aminobiphenyl-2,3-diol from Pseudomonas sp. strain CA10 (S. I. Sato, N. Ouchiyama, T. Kimura, H. Nojiri, H. Yamane, and T. Omori, J. Bacteriol. 179:4841-4849, 1997), and 2,3-dihydroxyphenylpropionate 1,2-dioxygenase (MhpB) of Escherichia coli (E. L. Spence, M. Kawamukai, J. Sanvoisin, H. Braven, and T. D. H. Bugg, J. Bacteriol. 178:5249-5256, 1996). The ring fission product formed from OH-DDVA by LigZ developed a yellow color with an absorption maximum at 455 nm, suggesting meta cleavage. Thus, LigZ was concluded to be a ring cleavage extradiol dioxygenase. LigZ activity was detected only for OH-DDVA and 2,2',3,3'-tetrahydroxy-5,5'-dicarboxybiphenyl and was dependent on the ferrous ion.

Inhibitory effect of habu antivenom on fibrinopeptide A release induced by Trimeresurus flavoviridis crude venom.

The correlation between the clotting activity of crude venom and concentration of fibrinopeptide A (FPA) released by the crude venom in rabbit plasma was evaluated and expressed as the coefficient of correlation (r = 0.850). The venom-induced FPA release was inhibited by habu antivenom. For such inhibition of FPA release, the correlation between the concentration of habu antivenom (Y) and that of crude venom (X) could be expressed by the equation Y = 7.115 + 0.709X. An absence of venom-induced FPA release in rabbit plasma had suggested that the clotting activity of crude venom could be neutralized by the habu antivenom. It is suggested that determinations of the FPA level in the plasma are effective in providing an indication of the reliability for serotherapy using habu antivenom.

[The correlation between the outbreaks of asthma attack and meteorologic parameters in Okinawa].

The correlation between the outbreaks of asthma attack and meterologic parameters was analyzed in Okinawa island which belongs to the subtropics. The epidemiologic outbreaks of asthma was investigated for 2 years from the asthma diaries described by 27 patients. The severity of asthma attack was expressed as the asthma score on the basis of asthma diaries. The number of patients carried to hospitals by ambulance on asthma attacks was investigated for 3 years. Two-by-two contingency tables were computed for the meteorologic parameters and analyzed with the method of chi-square test. From the view point of asthma scores, the total scores of 27 patients were increased when a mean and a minimum temperature were respectively higher than each mean value in the period of investigation (p < 0.05, respectively). From the view point of the number of patients carried to hospitals by ambulance on asthma attacks, it was suggested that asthma attacks tended to occur when a mean, a maximum and a minimum temperature, and a vapor pressure were lower than each mean value (p = 0.0001, p = 0.0001, p = 0.0001, p = 0.0002), and a barometric pressure was higher than a mean value in the period of investigation (p = 0.0016). From the further analysis of these data by multiple regression analysis, it was suggested that the number of patients carried to hospitals by ambulance on asthma attacks was influenced by low temperature. In addition, it was suggested that the changes of meteorologic parameters on the passing over of typhoon, especially, the decrease of temperature and barometric pressure, were related to induce asthma attacks.

Inhibition of habutobin activities by habu antivenom.

This study investigated whether habu antivenom inhibits the clotting activity of habutobin, a thrombin-like enzyme from Trimeresurus flavoviridis venom. Habu antivenom, which is available as a commercial antibody against the crude venom of T. flavoviridis, has been used to treat envenoming by T. flavoviridis (the habu snake). The present study was undertaken to determine whether habu antivenom inhibits the activities of habutobin, which involve digestion of the A alpha chain and release of fibrinopeptide A (FPA) in rabbit fibrinogen. The results of sodium dodecyl sulfate-polyacrylamide gel electrophoresis demonstrated that habu antivenom inhibited the habutobin-induced digestion of the A alpha chain in rabbit fibrinogen. The results of FPA measurements using competitive enzyme-linked immunoassay (CELIA) revealed that habu antivenom inhibited the release of FPA from rabbit fibrinogen induced by habutobin. In addition, a correlation was noted between the digestion of the A alpha chain and release of FPA from rabbit fibrinogen. Analysis of the inhibition kinetics of habu antivenom against the habutobin activity yielded a competitive double-reciprocal plot.

Habutobin splits the Arg16-Gly17 bond in the A alpha chain of rabbit fibrinogen.

We reported previously that habutobin, a thrombin-like enzyme from Trimeresurus flavoviridis venom, clotted only rabbit fibrinogen, whereas human, monkey, bovine, dog, rat and guinea-pig fibrinogens were unaffected. In the present study, we investigated the cleavage site of the rabbit A alpha chain by habutobin. The fibrinopeptide released by habutobin was identical to the fibrinopeptide A released by thrombin, and its amino acid sequence corresponded to A alpha 1-16 of rabbit fibrinogen. It was clarified therefore that habutobin cleaves the Arg16-Gly17 bond in the A alpha chain of rabbit fibrinogen.

Inhibitory effect of azelastine hydrochloride and suplatast tosilate on airway responses in sensitized rats following exposure to antigen.

In the present study, we examined the relationship between the increase in respiratory resistance following exposure to antigen and the IgE level in the identical rate sensitized with DNP-As. Additionally, we investigated the effects of the antiallergic drugs, suplatast tosilate and azelastine hydrochloride, which have been reported to suppress the production of IgE, on the increase in respiratory resistance in rats following exposure to antigen. The IgE antibody level rose to its highest value on day 10 during the course of sensitization with DNP-As, and decreased sharply on day 20. The changes of IgE antibody level in the azelastine hydrochloride-administered group were similar to those in the distilled water-administered group (control). In contrast, in the suplatast tosilate-administered group, the IgE antibody levels were lower than those in the control group at days 10 and 15. The ratio of increase in the respiratory resistance induced by the early and late phase responses in the control group reached its highest value on day 15, and then decreased gradually. In contrast, in both the azelastine hydrochloride and suplatast tosilate-administered groups, the ratio of increase in the respiratory resistance induced by the early and late phase responses remained almost unchanged, and was lower than that in the control group at day 15 or 20. In the present study, an increased peak of respiratory resistance was observed at 5 days after the appearance of an increased peak in the IgE level.

Production of a monoclonal dinitrophenyl-specific rat IgE and establishment of an IgE capture ELISA for estimating the concentration of rat IgE antibodies to dinitrophenyl-Ascaris suum.

A hybridoma producing monoclonal rat IgE antibodies of antidinitrophenyl (anti-DNP) specificity was generated by fusion of Sp2/0-Ag 14 (SP2) mouse myeloma cells and spleen cells from a DNP-Ascaris-sensitized Brown-Norway rat. Subsequently, the supernatant of the hybridoma (FE-3) was applied to an affinity column of DNP-bovine serum albumin-Sepharose 4B. The adsorbed protein fraction was pooled, concentrated, and further purified using Sephadex G-200. The molecular weight of the isolated protein was approximately 200,000 by SDS-PAGE, and the protein reacted with peroxidase (POD) mouse antirat myeloma IgE on Western blotting. Rabbit antibodies against DNP-specific rat IgE were also prepared by immunizing Japanese white rabbits with monoclonal DNP-specific rat IgE. These antibodies against DNP-specific rat IgE were applied to an affinity column of normal rat serum-Sepharose 4B and monoclonal DNP-specific rat IgG2b-Sepharose 4B to remove any other reactive substances apart from IgE contained in the serum proteins of the rat sensitized with DNP-Ascaris. On ELISA, it was found that the specificity of POD rabbit antibodies against DNP-specific rat IgE for monoclonal DNP-specific rat IgE was the same as that for rat myeloma IgE (IR 162). In addition, determinations of the monoclonal DNP-specific rat IgE revealed that the sensitivity of ELISA using POD-rabbit antibodies against DNP-specific rat IgE [POD-RA(DNP)RE] was higher than that using POD goat antibodies against rat myeloma IgE. Furthermore, an IgE capture ELISA employing the above-mentioned RA(DNP)RE was established for estimating the rat IgE antibodies to DNP-Ascaris suum. A good correlation was found between the antigen-specific IgE antibodies in the serum of Wistar rats estimated by this IgE capture ELISA and those estimated by passive cutaneous anaphylaxis.

Habutobin releases plasminogen activator (U-PA) from bovine pulmonary artery endothelial cells.

Habutobin is a thrombin-like enzyme, contained in the venom of Trimeresurus flavoviridis, which has the strongest toxic effect in cases of habu bite. The present study was undertaken to examine the effect of habutobin on the release of plasminogen activators using cultured endothelial cells of the bovine pulmonary artery. The chemical characteristics of the plasminogen activators released into the conditioned medium were determined by fibrin autography and immunological analysis. A chromogenic substrate (S-2251) microassay was employed for quantitative estimation of the plasminogen activator activity in the conditioned medium and euglobulin fraction derived from the conditioned medium. The levels of plasminogen activator inhibitor released into the conditioned medium were determined by reverse fibrin autography. Fibrin autography revealed that cultured bovine pulmonary artery endothelial cells spontaneously released tissue-type plasminogen activator (t-PA) and urokinase-type plasminogen activator (u-PA) into the conditioned medium with no stimulus. Exposure of confluent cultures to 50 nM habutobin, however, induced a time-dependent increase in the level of plasminogen activator activity in both the conditioned medium and euglobulin fraction, and the plasminogen activator activity in the euglobulin fraction at 24 hr was significantly higher than that in the control (P < 0.05). Reverse fibrin autography demonstrated that the lysis-resistant zone of the supernatant of the euglobulin fraction (habutobin exposure) was wider than that in the case of no stimulus. These findings suggest that habutobin induced a time-dependent increase in the levels of plasminogen activator and plasminogen activator inhibitor concomitantly.

A modification of the ELISA-double sandwich method for estimating the concentration of habutobin.

A monoclonal antibody to the thrombin-like enzyme, habutobin, was produced. An ELISA-double sandwich method employing this monoclonal antibody was devised as a method for determining the habutobin concentration in vitro. However, the absorbance of the control sample in such an ELISA-double sandwich procedure was too high to estimate low levels of the enzyme. The present study therefore attempted to establish a reliable ELISA-double sandwich method in which the absorbance of the control sample was lower than previously, and which had a high sensitivity, in order to determine the habutobin concentration in vitro and in vivo. The modification of the ELISA-double sandwich technique employing the monoclonal antibody against habutobin, the purified rat IgG against habutobin and POD-mouse anti-rat IgG2a, provided a reliable means of determining the habutobin levels in the circulating blood of rabbits.

[A case of successful tissue plasminogen activator in young-onset pulmonary embolism].

A 16-year-old boy was admitted to the hospital because of chest pain, dyspnea, and syncope. Physical examination revealed blood pressure of 100/60 mmHg, regular pulse of 120 beats/min, and respiratory rate of 30/min. Pulsation of the right ventricle was palpable in the left margin of the parasternum. An increased second sound was audible in the second inter-costal lesion of the left subclavicle mid-line. Results of blood tests were close to normal limits, except for slight leukocytosis and elevation of the LDH value. Analysis of artery blood gas showed hypoxia. The chest x-ray film showed cardiac enlargement. The value of systolic pulmonary artery pressure was estimated to be 47 mmHg by the cardiac echogram, which revealed enlargement of the right ventricle. Pulmonary embolism was suspected from the above findings. The value of pulmonary artery pressure was found to be 49/19 mmHg by Swan-Ganz catheter. Angiography of the pulmonary artery revealed filling defects of right in the right pulmonary artery. Tissue plasminogen activator was injected directly to the right pulmonary artery. After that, chest pain and dyspnea were relieved. In addition, arterial oxygen improved and pulmonary artery pressure decreased. At the 6th day after admission, the defect in the pulmonary artery angiography disappeared. Deep vein thrombosis of both femoral veins was recognized as a cause of pulmonary embolism by angiography of the femoral vein.

Inhalation of platelet-activating factor increases respiratory resistance in rats: determination by means of an astograph under nonanesthetized conditions.

Intratracheal administration of platelet-activating factor (PAF) to dogs, baboons, and humans has been shown to induce hyperreactivity of the airways and contraction of the smooth muscle. However, it has not yet been reported whether intratracheal administration of PAF to rats induces hyperreactivity. In the present study, the authors estimated the respiratory resistance of rats during intratracheal administration of PAF in order to evaluate the reactivity of the airways to PAF. In both the nonsensitized group and the sensitized group of rats, intratracheal administration of PAF induced an increase in respiratory resistance. The results obtained clarify that responsiveness to PAF exists in the airways of rats.