Epstein-Barr virus-associated lymphoproliferative disease after a cord blood transplant for Diamond-Blackfan anemia

A 7-year-old boy with Diamond-Blackfan anemia (DBA) developed lymphoproliferative disease (LPD) after a cord blood transplant (CBT). 3.1 x 107/kg mononuclear cells from an HLA one-locus mismatched CB were transplanted after conditioning with total body irradiation (8 Gy), cyclophosphamide (200 mg/kg) and antithymocyte globulin (10 mg/kg). Complete engraftment occurred on day 33 post transplant. Despite the resolution of grade II graft-versus-host disease (GVHD), he died of lymphoma on day 130 post transplant. The tumor was of donor origin, indicating clonal proliferation of Epstein-Barr virus (EBV)-infected B cells. This is the first report of EBV-LPD after CBT. Post-transplant LPD can be a serious EBV-associated complication of CB grafts. Bone Marrow Transplantation (2000) 25, 209-212.

COLLABORATIVE WORK TO EVALUATE TOXICITY ON MALE REPRODUCTIVE ORGANS BY REPEATED DOSE STUDIES IN RATS : 5)EFFECTS OF REPEATED DOSES OF FLUTAMIDE FOR 2 AND 4 WEEKS

Flutamide, a nonsteroidal antiandrogen, was administered orally to 8-week (for the 2 week study) and 6-week-old (for the 4 week study) male Crj:CD(SD) rats at dose levels of 0 mg/kg, 60 mg/kg and 200 mg/kg daily for 2 weeks or 4 weeks in order to determine whether a 2 week treatment period is sufficient for detection of drug effects on the male reproductive system. Flutamide treatment for 4 weeks resulted in decreased organ weights of the epididymides and prostate, decreased sperm counts and Leydig cell proliferation in the testes at 60 mg/kg and 200 mg/kg. Decreased sperm motility and histological lesions in the seminiferous tubules were observed at 200 mg/kg. Flutamide treatment for 2 weeks decreased organ weight of epididymides and prostate and caused Leydig cell proliferation in the testes at 60 mg/kg and 200 mg/kg. Decreased sperm counts and sperm motility, and histological lesions in seminiferous tubules were observed at 200 mg/kg. The results of this study showed that 2 weeks treatment with flutamide causes histological lesions of testes and disorders of sperm parameters similar to those observed with 4 weeks treatment, indicating that 2 weeks treatment is sufficient for detection of effects of flutamide on the male reproductive system.

Obesity does not influence electrocardiographic parameters in coronary patients

Although elevated body mass index (BMI) was found to be associated with QT prolongation in healthy subjects, electrocardiographic findings in coronary patients in relation to BMI have not been investigated. We studied 936 coronary patients whose electrocardiographic parameters were compared according to their BMI and found that BMI did not affect the overall QT duration, but QT dispersion was significantly higher in normal-weight coronary patients than in obese patients.

[Alpha 1-antitrypsin deficiency (Siiyama) with pulmonary emphysema]

A 44-year-old man was admitted to the hospital with dyspnea on exertion. Chest radiographs and pulmonary function tests showed evidence of pulmonary emphysema. Serum alpha 1-antitrypsin (alpha 1-AT) could not be detected by nephelometry, immuno-electrophoresis, or iso-electric focusing. However, allele-specific PCR revealed a genotype homozygotic for an alpha 1-AT deficient variant of the Siiyama allele. An elder sister of the proband was also a homozygous carrier of the Siiyama allele. The amino acid sequence for normal alpha 1-AT variants had been substituted by Arg101-Val213-Glu376 in the proband, demonstrating that the alpha 1-antitrypsin-deficient Siiyama variant in this pedigree was derived from M 1 (Val213).

Receptor specificity of influenza A viruses from sea mammals correlates with lung sialyloligosaccharides in these animals

The distribution of specific receptors on target organs is a major factor in the host range restriction of influenza A viruses. To assess the correlation between host receptors and the receptor specificity of influenza A viruses from sea mammals, we examined the receptors for influenza A virus in seal and whale lungs. A binding assay using two sialyloligosaccharide (SAalpha2,3Gal and SAalpha2,6Gal)-specific lectins showed that SAalpha2,3Gal, but not SAalpha2,6Gal, was found in both seal and whale lungs. Correspondingly, seal and whale influenza viruses preferentially recognized SAalpha2,3Gal, but not SAalpha2,6Gal. These results indicate that sialyloligosaccharides present at the replication site of influenza A viruses correlate with the receptor recognition of the viruses isolated from sea mammals.

Identification of the binding site for an alloantibody to von Willebrand factor which inhibits binding to glycoprotein Ib within the amino-terminal region flanking the A1 domain

An alloantibody to von Willebrand factor (vWF) which developed in a Japanese boy with type 3 von Willebrand disease has been characterized. The antibody was non-precipitating IgG and the main subclasses were IgG2 and IgG4. The antibody inhibited completely ristocetin-induced platelet aggregation (RIPA) and high shear stress-induced platelet aggregation (SIPA). Its predominant inhibitory role was focused, therefore, on the interaction between vWF and platelet gycoprotein Ib. The antibody reacted with a 52/48 kDa tryptic fragment of vWF (residues 449-728). No reaction was seen, however, with either a 39/34 kDa dispase fragment (480-718) or a recombinant vWF fragment (residues 465-728). These findings suggested that the essential epitope resided in the amino-terminal flanking region of the Al domain. We synthesized overlapping peptides corresponding to the region containing D3/A1 boundary. A peptide, residues 458-472, bound to the antibody and dose-dependently blocked the antibody binding to the 52/48 kDa fragment. The same peptide neutralized the inhibitory effect of the alloantibody on SIPA. The data are consistent with the presence of an epitope within residues 458-472 which reacted with the 52/48 kDa fragment. Furthermore, the specific component of the antibody, directed against residues 458-472, blocked vWF binding to GPIb in absence of exogenous agonist. Our results suggest that the region flanking the Al domain plays an important role in regulating vWF binding to GPIb.

Restricted diversification of T-cells in chronic active Epstein-Barr virus infection: potential inclination to T-lymphoproliferative disease

To assess the abnormal T-cell expansion in chronic active Epstein-Barr virus infection (CAEBV), T-cell antigen receptor (TCR) repertoire was analyzed in four patients with the disease. All fulfilled the diagnostic criteria of CAEBV, presenting with fever, hepatosplenomegaly, cytopenia, abnormal high titers of anti EBV-antibodies, and positive EBV genome of unknown cause. Southern blotting probed with EBV-terminal repeats and TCR Cbeta gene indicated clonal expansion of the infected cells in 3 and 2 patients, respectively. The number of CD4+ HLA-DR+ cells appreciably increased in patients 1 (59%) and 2 (24%), who had a coronary aneurysm and central nervous system involvement, respectively. TCR gene expression examined by the inverse polymerase chain reaction methods revealed that Vbeta gene usages were preferential in all patients (Vbeta7 and Vbeta12: patient 1, Vbeta4: patient 2, Vbeta13: patients 3 and 4), compared with those in healthy controls. Valpha18 gene expression was remarkably high in patients 1 and 2. Moreover, Jbeta gene expression was skewing in the reigning Vbeta clones in all patients. Vbeta4-Jbeta1.5 and Vbeta13-Jbeta1.5 genes were clonally expressed in patients 2 and 4, respectively. These results suggest that CAEBV is associated with the restricted diversity of T-cells, which may stem from the sustained expansion of oligoclonal T-cells possibly driven by conventional viral antigens, but not, superantigens. Although the study is limited by the small number of patients, the unbalanced T-cell repertoire might contribute to the evolution of T-lymphoproliferative disease, otherwise, imply the innate defective immunity to EBV in CAEBV patients.

[Peripheral blood stem cell transplantation--practices of mobilization and harvest]

Recently, mobilized peripheral blood stem cells (PBSC) are increasingly used as an alternative to bone marrow for engrafting procedures. Chemotherapy followed by recombinant human granulocyte-colony stimulating factor (rhG-CSF) or rhG-CSF alone are the most commonly used PBSC mobilization schedules. Current timing of apheresis has now been yet decided on time by flowcytometric analysis of CD34 positivity of peripheral blood whole white cell count. Because apheresis procedure has been established quite well, PBSC harvest procedure becomes fast, safe and stable.

Pituitary adenylate cyclase activating peptide induces cGMP-mediated relaxation in guinea-pig airways

The mechanism of relaxation of the guinea-pig trachea induced by pituitary adenylate cyclase activating peptide (PACAP)-27 was investigated. We examined whether modulators of nitric oxide (NO) and carbon monoxide (CO) affect PACAP-induced response of tracheal strips in vitro. Pretreatment with N omega-nitro-L-arginine methyl ester hydrochloride (L-NAME) and L-arginine (L-arg) had no effect, while 1H-[1,2,4] oxadiazolo[4,3-a]quinoxalin-1-one (ODQ), haemoglobin and zinc protoporphyrin IX (ZnPP-9) partially abolished the PACAP-induced relaxation. PACAP-27 elevated cyclic GMP level in airway smooth muscle tissue. These results indicate that PACAP-27 not only induces cyclic AMP-mediated responses, but also cyclic GMP-mediated responses in the airway. In addition, CO is related to the PACAP-induced elevation of cGMP level in the tracheal tissue.

[Possible contribution of alpha-adrenergic abnormalities to cerebral ischemia in the patients with sinus bradycardia. Analysis by pharmacologic autonomic nervous test]

BACKGROUND

Syncope of patients with bradyarrhythmia is perceived as severe sign of low cardiac output caused by bradycardia and as a major criteria for pacemaker implantation (PMI). However, it has been reported that PMI can not always prevent syncope; it has been suggested that not bradycardia but an abnormality of the autonomic nervous system plays a part in syncope.

PURPOSE

To investigate the relation between autonomic nervous dysfunction and syncope in cases of sinus bradycardia (SB).

SUBJECTS

Thirty-nine patients with SB were divided into two groups according to the presence (group S, n = 16, 46.9 +/- 20.0 years) or absence (group N, n = 23, 40.4 +/- 17.6 years) of syncope or presyncope.

METHODS

Corrected sinus node recovery time (CSNRT) was measured by electrophysiologic study. Pharmacologic autonomic nervous tests were performed as follows in a quiet room. Increased HR by application of 0.04 mg/kg atropine (para-tone), and by 0.004 microgram/kg/min isoproterenol divided by 0.004 (beta-sens) were evaluated, beta-tone was obtained by subtracting HR after application of propranolol (0.2 mg/kg) from that of atropine. Basal beta-sympathetic activity was evaluated by beta-sec that was obtained by beta-tone/beta-sens. Increased SBP by application of 0.4 microgram/kg/min phenylephrine divided by 0.4 (alpha-sens) was evaluated. alpha-tone was obtained by subtracting minimum SBP after 0.2 mg/kg phentolamine from SBP after application of propranolol. Basal alpha-sympathetic activity was evaluated by alpha-sec, that was obtained by alpha-tone/alpha-sens.

RESULT

There were no significant differences in basal clinical characteristics (age, sex, cardiac function) between the groups. The parameters of the functions of parasympathetic and beta-sympathetic receptors (para-tone, beta-sens, beta-tone, beta-sec) showed no significant differences between the groups, alpha-sens was attenuated (P < 0.01) and alpha-sec was augmented (P < 0.0001) significantly in group S.

CONCLUSION

It was suggested that syncope or presyncope in SB patients could be attributed to failure of vasoconstriction mediated by alpha-sympathetic receptor but to severity of sinus node dysfunction.

Recovery of cardiac norepinephrine concentration and tyrosine hydroxylase activity by the central alpha2-adrenoceptor agonist guanabenz in rats with aortic constriction

Depletion of cardiac norepinephrine has been reported in cardiac hypertrophy. This depletion causes less support for cardiac output in response to sympathetic nerve activation. The central nervous system is thought to be involved in this abnormality. Correction of this abnormality is expected to restore proper support for the heart. Clipping of the ascending aorta or a sham operation was performed in 10-week-old rats. At 4 weeks after the operation, the left ventricular norepinephrine concentration in clipped rats decreased (p<0.01). The clipped rats and sham-operated rats were treated with either guanabenz (1 mg/kg) or a vehicle for 4 weeks starting from fifth postoperative week. The level of left ventricular norepinephrine increased more in clipped rats treated with guanabenz (469+/-37 ng/g) than in clipped rats treated with a vehicle (325+/-28 ng/g). The norepinephrine concentration in the left ventricle recovered significantly after the treatment with guanabenz (p<0.001). Tyrosine hydroxylase activity in the left ventricle also recovered after treatment with guanabenz (p<0.01). Modulation of sympathetic nerve tone by the alpha2-adrenoceptor agonist restored cardiac norepinephrine concentration and tyrosine hydroxylase activity. This could be a new approach to the treatment of heart failure.

In vitro reconstitution of the tracheal epithelium

We have developed a unique in vitro reconstitution system for tracheal epithelia of guinea pigs. In the system, a human amnion membrane was used as a basement membrane and the tracheal epithelial cells were cultured on the epithelial side of the membrane. Three weeks later, the tracheal fibroblasts were co-cultured on the serosal side of the amnion membrane and the culturing was continued for an additional 10 d. The morphology of the cultured epithelial cells consisted of a pseudostratified columnar ciliated epithelium from cuboidal ciliated epithelium during the last 10 d of the culture period. Epithelial cells included both goblet-like and basal cells. In addition, the frequency of each type of differentiated cells was almost identical to that of in vivo tracheas. Interestingly, the same results were obtained when the conditioned medium of the tracheal fibroblasts was used instead of the fibroblasts themselves. These results suggest that epithelial-mesenchymal interaction is likely involved in growth and differentiation of epithelial cells in vivo in a soluble factor(s)-mediated manner. As well as the epithelial cells, the fibroblasts also formed a multilayer during the last 10 d of co-culturing. This indicates that in vitro reconstitution of tracheal epithelia is achieved without addition of any exogenous growth or differentiation factors. The reconstitution system is shown to be useful for investigating the cellular and molecular interaction of epithelial and mesenchymal cells. Possible applications of the culture system and possible factors involved in growth and differentiation of epithelial cells are discussed.

Fibromuscular dysplasia involving coronary arteries--a case report

The authors report a young patient with fibromuscular dysplasia involving multivessels including coronary arteries. If young patients have chest pain on effort, fibromuscular dysplasia of coronary arteries must be considered. As fibromuscular dysplasia is a chronic progressive disease and some cases progress rapidly in a few months, careful follow-up and comprehensive medical management may be necessary in such patients.

Effects of airway inflammation on cough response in the guinea pig

We have developed a guinea pig model for cough related to allergic airway inflammation. Unanesthetized animals were exposed to capsaicin aerosols for 10 min, and cough frequency was counted during this period. The cough evaluation was performed by the following three methods: visual observation, acoustic analysis, and monitoring of pressure changes in the body chamber. These analyses clearly differentiated a cough from a sneeze. To elucidate the relationship between cough response and airway inflammation, animals were immunosensitized and multiple challenged. Sensitized guinea pigs presented no specific changes microscopically, but multiple-challenged animals showed an increased infiltration of inflammatory cells into the airway. Cough number in response to capsaicin increased significantly from 4.7 +/- 1.4 coughs/10 min in normal animals to 10.6 +/- 2.0 coughs/10 min in sensitized animals and further to 22.8 +/- 1.3 coughs/10 min in multiple-challenged animals. This augmented cough frequency was significantly inhibited by the inhalation of tachykinin-receptor antagonists and by oral ingestion, but not inhalation, of codeine phosphate. The results suggest that airway inflammation potentiates an elevation of cough sensitivity in this model.

[Changes of 24-h Holter monitor recordings in association with interferon alpha therapy for chronic hepatitis C]

We examined cardiovascular complication of interferon (IFN) therapy in 23 patients with chronic hepatitis C who did not have cardiac disease prospectively. Twenty four-h Holter monitor recordings were performed before and during IFN therapy. Seven of these patients (30%) showed abnormalities on their 24-h Holter monitoring recordings. Premature ventricular contraction (PVC) occurred in two patients, intermittent WPW syndrome in one, and ST-T change in four. Only one patient with PVC complained of palpitation. These complications were not severe and immediately after IFN therapy was stopped. There was no correlation between Holter ECG abnormalities and sex, age, quantity of HCV, or 2-5 oligoadenylate synthetase activity. It was suggested that cardiovascular complications caused by IFN therapy occurred more frequently than expected. However, diagnosis of these complications is difficult because most patients have no subjective symptoms and there is scarcely any change in laboratory test results. Careful observation of patients may be required during IFN therapy regardless of cardiovascular symptoms.

The role of gammadelta T cells in induction of bacterial antigen-specific protective CD8+ cytotoxic T cells in immune response against the intracellular bacteria Listeria monocytogenes

The role of T-cell receptor (TCR) gammadelta T cells in the induction of protective TCR alphabeta T cells against infection by the intracellular bacteria Listeria monocytogenes was analysed. We found that depletion of gammadelta T cells by anti-TCR delta monoclonal antibody treatment before intravenous immunization of mice with a sublethal dose of viable L. monocytogenes resulted in reduction of protection against secondary challenge infection in the immunized mice. The gammadelta T-cell depletion also reduced induction of protective alphabeta T cells capable of transferring the protection against challenge infection of L. monocytogenes into naive mice. Furthermore, the protective T cells that were affected by the gammadelta T-cell depletion were suggested to be CD8+ cytotoxic T cells rather than CD4+ T cells by the following observations. First, induction of cytotoxic T lymphocytes specific to a L. monocytogenes-derived H-2Kd-restricted peptide (listeriolysin O 91-99) was significantly suppressed by gammadelta T-cell depletion before immunization. Second, gammadelta T-cell depletion did not affect cytokine production and proliferation of T cells from immunized mice in response to in vitro stimulation with heat-killed Listeria which preferentially stimulates CD4+ T cells. Third, CD8+ alphabeta T cells from control immunized mice transferred protection against infection of L. monocytogenes into naive mice but only a limited degree of protection was transferred by CD8+ T cells from the gammadelta T-cell-depleted immunized mice; and fourth, CD4+ alphabeta T cells from the gammadelta T-cell-depleted mice transferred a similar level of protection as those from the control immunized mice. All these results suggest that gammadelta T cells participate in establishment of protective immunity against intracellular bacteria by supporting priming of bacterial antigen-specific CD8+ cytotoxic T cells.

[Autonomic nervous function of the patients with neurally mediated syncope]

Although diagnosis of neurally mediated syncope (NMS) using head-up tilt (HUT) test has been established, the exact mechanism of NMS has not yet been elucidated. We evaluated beta and alpha-adrenergic function in NMS patients by pharmacological autonomic function test. The alpha-adrenergic sensitivity of NMS patients was significantly lower than that of control subjects. The patients who need low dose isoproterenol for provocation of syncope showed higher beta-adrenergic sensitivity than patients who developed syncope without isoproterenol. Thus, pharmacological autonomic function test was useful for evaluation of NMS patients.

Functional replacement of OprJ by OprM in the MexCD-OprJ multidrug efflux system of Pseudomonas aeruginosa

For characterization of the MexCD-OprJ efflux system of Pseudomonas aeruginosa involved in resistance to fluoroquinolones and the fourth-generation cephems, we constructed mexC, mexD or oprJ mutants from the nfxB-type PAO strains by insertion mutagenesis. The gene products in the resultant mutants were examined by immunoblot assay using murine and rabbit antibodies developed against purified protein and synthetic oligopeptides. Susceptibility of the mexC (MexC- MexD- OprJ-) and mexD (MexC+ MexD- OprJ-) mutants to fluoroquinolone and the fourth-generation cephems was comparable to that of the wild-type strain PAO1. However, the oprJ mutant (MexC+ MexD+ OprJ-) was still less susceptible than PAO1, since a MexCD-OprM chimera system, which generated from a functional assist of the constitutively expressed OprM, can function in the efflux of the antimicrobial agents in the oprJ mutant. In fact, transformation of the oprJ mutant with an OprM-expression plasmid decreased the former's susceptibility to the levels exhibited by the nfxB mutant without affecting the substrate specificity of MexCD-OprJ.

[Effect of carbon tetrachloride-induced hepatic injury on stereoselective N-demethylation of chlorpheniramine by rat hepatic cytochrome P450 2C11 isozyme]

We examined the effect of a carbon tetrachloride (CCl4)-induced hepatic injury on the stereoselective N-demethylation of RS-(+/-)-chlorpheniramine (Chp) by cytochrome P450 (CYP) 2C11 isozyme. In the non-treated rat liver microsomes, the stereoselective N-demethylation of racemic Chp was observed. However, in the CCl4-treated (0.5 ml/kg, i.p.) rat liver microsomes, the N-demethylation activities of S-(+)- and R-(-)-Chp decreased continuously up to the third day after the treatment with CCl4, and reached about 9 and 13% of control values, respectively, and the stereoselective N-demethylation of Chp was not observed. Moreover, in the liver microsomes at the 7th day after the treatment with CCl4, the N-demethylation activities of both enantiomers recovered to an original level, and the stereoselective N-demethylation of Chp was again observed. The addition of 30 microliters of the anti-rat CYP2C11 serum to the reaction mixture containing 1 mg of microsomal protein inhibited the formation of monodesmethylchlorpheniramine (DMChp) from both enantiomers to 74 and 57% of the control values for S-(+)- and R-(-)-Chp, respectively. In the liver microsomes of a male rat at the 1st day after the treatment of CCl4, the addition of the anti-rat CYP 2C11 serum (30 microliters) also caused 25% inhibition of the formation of DMChp from S-(+)-Chp, but anti-rat CYP2C11 had no inhibitory effect on the rates of microsomal N-demethylation of R-(-)-enantiomer. On the other hand, in the liver microsomes of a male rat at the 7th day after the treatment with CCl4, the anti-rat CYP2C11 serum had an inhibitory effect on the rates of microsomal N-demethylation of either S-(+)- or R-(-)-enantiomers again. Moreover, it was confirmed by Western blotting analysis that the density of the stained bands of CYP2C11 in the liver microsomes from male rats at the 1st, 2nd and 3rd days after the treatment with CCl4, was thinner than that from non-treatment male rats. These results indicated that the changes of N-demethylation activities of Chp in the CCl4-induced hepatic injury were due to the variation of microsomal CYP2C11.

DNA replication cycle in parthenogenetically developing eggs of the starfish Asterina pectinifera

Starfish oocytes artificially activated by a calcium ionophore will develop normally if the formation of polar bodies is suppressed. In the present paper, schedules of the DNA replication period (S phase) of these parthenogenotes were explicitly timed using 5-bromo-2'-deoxyuridine (BrdU) and anti-BrdU monoclonal antibody. Their schedule of S phase was identical to that of fertilized eggs. Consequently, an S phase regulation system is triggered even in parthenogenotes raised by dual treatment of egg activation and polar body suppression. The S phase schedule of parthenogenotes confirms the temporal pattern of chromosome duplication, observed by other researchers, leading to tetraploid parthenogenotes. The S phase determination also provides a basis for argument concerning the number of centrioles participating in parthenogenetic development. If polar body formation of activated eggs was not suppressed, the first S phase was normal, but the second S phase did not recur on time. A rigidly regulated system of DNA replication cycle, which should be an essential prerequisite for parthenogenesis, thus requires the content of polar bodies.

Characterization of the MexC-MexD-OprJ multidrug efflux system in DeltamexA-mexB-oprM mutants of Pseudomonas aeruginosa

Expression of the multidrug efflux system MexC-MexD-OprJ in nfxB mutants of Pseudomonas aeruginosa contributes to resistance to fluoroquinolones and the "fourth-generation" cephems (cefpirome and cefozopran), but not to most beta-lactams, including the ordinary cephems (ceftazidime and cefoperazone). nfxB mutants also express a second multidrug efflux system, MexA-MexB-OprM, due to incomplete transcriptional repression of this operon by the mexR gene product. To characterize the contribution of the MexC-MexD-OprJ system to drug resistance in P. aeruginosa, a site-specific deletion method was employed to remove the mexA-mexB-oprM region from the chromosome of wild-type and nfxB strains of P. aeruginosa. Characterization of mutants lacking the mexA-mexB-oprM region clearly indicated that the MexC-MexD-OprJ efflux system is involved in resistance to the ordinary cephems as well as fluoroquinolones and the fourth-generation cephems but not to carbenicillin and aztreonam. Rabbit polyclonal antisera and murine monoclonal antibody against the components of the MexA-MexB-OprM system were prepared and used to demonstrate the reduced production of this efflux system in the nfxB mutants. Consistent with this, transcription of the mexA-mexB-oprM operon decreased in an nfxB mutant. This reduction appears to explain the hypersusceptibility of the nfxB mutant to beta-lactams, including ordinary cephems.

Molecular cloning and characterization of Ca2+-dependent inducible nitric oxide synthase from guinea-pig lung

We have isolated a full-length cDNA for an inducible nitric oxide synthase (iNOS) from guinea-pig lung. The cDNA has a 3447 bp open reading frame encoding 1149 amino acid residues. The deduced amino acid sequence is approx. 80% identical with iNOS of human epithelial cells and murine macrophages. Consensus recognition sites for cofactors are highly conserved. COS cell lysate transfected with the guinea-pig iNOS shows significant levels of nitric oxide synthase (NOS) activity, and this is inhibited by 79% by chelation of Ca2+ ions. The NOS activity is restored in a concentration-dependent manner by increasing the free Ca2+ level. The NOS activity is also inhibited by trifluoperazine, a calmodulin antagonist, which suggests that the Ca2+ dependence is due to Ca2+-dependent calmodulin binding to the enzyme. Northern blot analysis reveals that the cloned iNOS mRNA is expressed in the lung and the colon in normal guinea pigs. Stimulation in vivo by lipopolysaccharide induces the expression of iNOS in the kidney, the spleen and the colon, but in the lung the same stimulation decreases its expression. These results suggest that the cloned guinea-pig iNOS is distinct in characteristics and expression from previously described iNOS forms.