Untreated Graves' but not remission Graves' immunoglobulin G preparations increase intracellular Ca2+ in FRTL-5 thyroid cells

We compared immunoglobulin G (IgG) preparations obtained from untreated Graves' patients with those from Graves' patients in remission and normal subjects in terms of their activity to stimulate the phospholipase C-Ca2+ signaling. Ca2+ mobilizing activity of the untreated Graves' IgG preparations in FRTL-5 thyroid cells was statistically (P < 0.01) and significantly higher than the activity of normal IgG preparations, whereas there was no significant difference in the activity between the remission Graves' and normal IgG preparations. Digital video imaging of fura2-loaded FRTL-5 cells confirmed that the Ca2+ mobilizing action of the untreated Graves' IgG preparations is an intracellular event. Phospholipase C activation by the untreated but not remission Graves' IgG preparations was statistically higher than that by normal IgG preparations. Involvement of the phospholipase C activation in the Ca2+ response mechanism was confirmed by the enhancement of the Ca2+ response by an adenosine derivative, N6(L-2-phenylisopropyl)adenosine (PIA) which can potentiate agonist-induced phospholipase C activation but not the Ca2+ mobilization itself. The Ca2+ response to the IgG preparations did not show a significant correlation with their cAMP response (TSAb). Therefore, the Ca2+ response to Graves' IgG preparations may be utilized as a functional marker for Graves' disease in addition to TSAb.

Complications of childhood Sjögren syndrome

Sjögren syndrome (SS) is a common disorder in adults and involves both glandular and extraglandular systems. We report here four cases of childhood SS complicated by chronic thyroiditis, interstitial nephritis or sweat gland inflammation. Additionally, in one of these cases, the central nervous system was involved. All of these complications are common in adult cases.

CONCLUSION

Childhood SS is a systemic "ductilitis" or "exocrinopathy" with complications which are commonly observed in adult cases.

Interferon-alpha potentiates the antiproliferative activity of CPT-11 against human colon cancer xenografts in nude mice

Recently cytokines have been reported to potentiate the antiproliferative effects of chemotherapeutic agents against a variety of malignant tumors. We studied the antiproliferative effect of recombinant human interferon-alpha (rHuIFN-alpha) and CPT-11 on transplantable human colon cancer H-110 in nude mice. CPT-11 was administered to the H-110-bearing nude mice intraperitonealy every 4 days and rHuIFN-alpha was administered subcutaneously every day. The weight of the individual tumor was estimated by the tumor size. The cell cycle was analyzed by flow cytometry. The single administration of rHuIFN-alpha failed to show any antiproliferative activity. The antiproliferative effects of CPT-11 alone were observed in a dose and time dependent manner. This antiproliferative activity was markedly (p < 0.05) enhanced by combination with rHuIFN-alpha. Flow cytometric analysis revealed that treatment with rHuIFN-alpha accumulated cells in the S phase. rHuIFN-alpha can enhance the antiproliferative effects of CPT-11, probably through the accumulation of the tumor cells in the S phase.

Immunohistochemical detection of proliferating cell nuclear antigen (PCNA) in 23 cases of ameloblastoma

Ameloblastoma is the most frequent odontogenic tumour. It occurs mainly in the mandible and grows expansively. The treatment of ameloblastoma, which influences the prognosis, is decided in consideration of many factors, especially the age and size of the tumour. Conservative treatment sometimes leads to the recurrence of tumours and poor prognosis, but the relationships between the prognosis and the cytological features of tumour cells are still unclear. In the present study, we examined the immunohistochemical detection of proliferating cell nuclear antigen (PCNA) in 23 cases of ameloblastoma and evaluated the correlation between the positive index of PCNA and the clinical and histological character. Our results revealed the higher the age of the patient the greater was the incidence of a positive index of PCNA. It was also shown that the mean positive PCNA index in the follicular type (34.56 +/- 14.00 S.D.) was higher than that of the plexiform type (24.436 +/- 15.74 S.D., P < 0.10). The cystic type showed a low positive PCNA index (14.75 +/- 8.41 S.D.). In the follicular type, the localisation of PCNA-positive cells was different according to the histological patterns of tumours. Additionally, the positive indices of the same patient differed at different periods of treatment.

[Simultaneous isolation of MRSA and Pseudomonas aeruginosa using a novel selective and differential PMAC agar]

PMAC agar, a novel, selective and differential medium has been developed and was subjected for evaluation of its selective and differential capability of methicillin resistant Staphylococcus aureus (MRSA) and Pseudomonas aeruginosa from other bacteria such as Bacillus, Micrococcus, Gram-negative bacteria and drug resistant ones. Growth of MRSA and P. aeruginosa on PMAC agar was facilitated and their colonies were easily differentiated. Colonies of MRSA after 24 approximately 48 h incubation at 35 degrees C were small (2 to 4 mm in diameter), smooth and egg-yolk reaction positive. On the other hand, P. aeruginosa with pigment production (pyocianin, fluorescin or pyomelanin) formed large (2.5 to 7.0 mm in diameter), brownish black or brown colonies with a creamy edge. PMAC agar did not allow to grow unwanted bacteria tested except certain species formerly classified to Pseudomonas such as Burkholderia and Stenotrophomonas. However multi-drug resistant strains such as Enterobacter cloacae, Serratia marcescens and Acinetobacter calcoaceticus formed extremely small colonies. PMAC agar is recommended as a novel, useful medium for isolation, differentiation and presumptive identification of MRSA and P. aeruginosa from clinical and environmental sources.

Evidences for involvement of cyclooxygenase-2 in proliferation of two gastrointestinal cancer cell lines

Cyclooxygenase (COX) consists of two isozymes, COX-1 and COX-2. The roles of these isozymes in the gastrointestinal tract are unknown. We investigated messenger RNA expression of the COX-1 and COX-2 genes in the gastrointestinal cancer cell lines MKN28, MKN45, KATO III CACO-2, DLD-1 and LoVo. These cell lines expressed comparable levels of COX-1 mRNA, although their expression of COX-2 varied. Therefore, we studied the effects of NS-398 and indomethacin, specific and non-specific inhibitors for COX-2, on proliferation of the cell lines. Both of the inhibitors suppressed proliferation of the two cell lines that highly expressed COX-2 (MKN45 and CACO-2). However, these inhibitors exerted minimal effects on proliferation of the other cell lines, which expressed significantly lower levels of COX-2. Therefore, it was proposed that COX-2 participates in proliferation of cancer cells because of over expression of the COX-2 gene.

Human cerebral activity with increasing inspiratory force: a study using positron emission tomography

Human cerebral activity with increasing inspiratory force: a study using positron emission tomography. J. Appl. Physiol. 81(3): 1295-1305, 1996.--The major aim of this study was to use positron emission tomography (PET) to assess dose-dependent effects of inspiratory loads on relative regional cerebral blood flow as an indication of neuronal activation and recruitment. Six normal men underwent H2 15O-PET scanning during unloaded breathing and with external inspiratory loads (generating mouth pressures of -5, -10, and -15 cmH2O); positive-pressure ventilation against relaxed respiratory muscles acted as control. During unloaded breathing, the supplementary motor area was significantly activated. With the addition of the smallest load, activations also occurred in the right premotor area and bilaterally in the superolateral motor cortex (MI) in areas previously shown to be activated with deeper breathing. There was little further change in these areas with greater loads. Additional force-related activations occurred in the inferolateral sensorimotor cortex, parietal cortex, and midbrain/hypothalamus. The results suggest that volitionally induced increases in inspiratory muscle force are achieved via a complex integration of neuronal activations in cortical and subcortical regions associated with motor control.

Decreased serum 1,5-anhydroglucitol in nondiabetic subjects with a family history of NIDDM

OBJECTIVE

To investigate the effect of a family history of NIDDM on HbAlc and serum 1,5-anhydroglucitol (AG) in nondiabetic subjects.

RESEARCH DESIGN AND METHODS

A 75-g oral glucose tolerance test was performed; 258 subjects with normal glucose tolerance and 106 subjects with impaired glucose tolerance (IGT) were selected HbAlc and serum AG were compared between subjects with and without a family history of NIDDM. The relationships between age, BMI, HbAlc, serum AG, fasting and 2-h plasma glucose, and urinary glucose were also examined using principal component analysis with a varimax rotation.

RESULTS

In the normal group, only serum AG was lower in subjects with a positive family history than in those with no family history. On the other hand, in the IGT group, subjects with a positive family history were younger and had a higher 2-h plasma glucose, a higher urinary glucose, and a lower serum AG than those with no family history, whereas there was no difference in HbAlc. Principal component analysis identified three factors. The first factor, a linear combination of HbAlc and fasting plasma glucose, was labeled an average glycemic factor. The second factor, which included serum AG, 2-h plasma glucose, and urinary glucose, was labeled an oscillatory glycemic factor. The third factor, which contrasted age against BMI, was labeled an environmental factor.

CONCLUSIONS

Serum AG is related to glycosuria even among nondiabetic subjects, and its concentrations are decreased in those with a family history of NIDDM. Our results suggest that serum AG rather than HbAlc reflects early metabolic abnormalities in these subjects.

Mutation in DNA gyrase of norfloxacin-resistant clinical isolates of Neisseria gonorrhoeae

BACKGROUND AND OBJECTIVES

Recently a rapid decrease in the susceptibility of Neisseria gonorrhoeae isolates to fluoroquinolones has occurred and gonococcal fluoroquinolone resistance is now a significant problem in the treatment of gonorrhoea in Japan. Thus, in order to investigate the quinolone resistance mechanisms in clinical isolates of N gonorrhoeae we studied an alteration in the DNA gyrase subunit A (GyrA) which is well-known as a common mechanism of bacterial quinolone resistance.

MATERIALS AND METHODS

Four clinical isolates of N gonorrhoeae resistant to norfloxacin and 5 strains susceptible to norfloxacin, including 2 clinical isolates and 3 WHO reference strains, were tested in this study. To identify mutations in the GyrA genes of gonococcal strains, polymerase chain reaction and direct DNA sequencing were performed.

RESULTS

A single base change (serine codon TCC changed to phenylalanine codon TTC), which resulted in an amino acid change in GyrA at position 91, was identified in all 4 norfloxacin-resistant strains for which the MICs of norfloxacin ranged from 1.0 to 8.0 micrograms/ml, while no mutation within GyrA was detected in 5 norfloxacin-susceptible strains for which the MICs of norfloxacin ranged from 0.004 to 0.063 microgram/ml.

CONCLUSIONS

The results from this study suggest that the serine-91 to phenylalanine substitution in GyrA is probably an essential mutation in fluoroquinolone resistance in clinical isolates of N gonorrhoeae.

Myocardial infarction in myxoma patients with normal coronary arteries. Case reports

Three cases of patients with cardiac myxoma who had attacks of acute myocardial infarction are presented. Cineangiographic study showed normal coronary arteries. Immunohistochemical and serologic examination revealed that both interleukin-6 and interleukin-8 were secreted in cardiac myxoma. The authors discuss the relation between these cytokines and myocardial infarction with normal coronary arteries.

Tracheal, circulatory, and respiratory responses to femoral nerve stimulation

Tracheal, circulatory, and respiratory responses to electrical stimulation of the afferent nerve from the hindlimb were analyzed in decerebrate, paralyzed, and mechanically ventilated dogs. Tension of the tracheal smooth muscle (TSM), arterial blood pressure, and phrenic nerve activity (PNA) were measured during stimulation of the proximal end of the transected femoral nerve (FNS) with train pulses (duration; 0.5 ms, frequency; 40 Hz). With low intensity (e.g., 0.62 V) FNS, TSM exhibited relaxation, arterial pressure decreased, and neural respiratory output (NRO) was reduced (3 of 8 dogs) or unchanged (5 of 8 dogs). With increases in stimulus intensity, TSM always exhibited relaxation while arterial pressure and NRO exhibited excitatory responses almost at the same thresholds (approximately 5 V). The TSM relaxation and the excitatory NRO and arterial responses augmented with increases in stimulus intensity up to 16 times of threshold of the excitatory NRO response. TSM response was blocked by intravenous atropine but pressor response and phrenic response were not. The arterial response disappeared after administration of a ganglionic blocker. These findings suggest that TSM, arterial pressure, and PNA may be controlled by one neuronal mechanism during high intensity FNS, but that arterial pressure and PNA may be modified by another mechanism in an inhibitory direction when the stimulus intensity is low. This study suggested the existence of a neural mechanism which controls the airway and cardiorespiratory systems properly to execute exercise. Physiological significance of the responses to low intensity femoral nerve stimulation was uncertain.

Inhibition of leukotriene synthesis by honokiol in rat basophilic leukemia cells

The effects of honokiol, a diphenyl compound extracted from a Chinese herbal medicine, on leukotriene (LT) synthesis were evaluated in rat basophilic leukemia (RBL) cells. The production of LTC4 and LTB4 stimulated by the Ca2+ ionophore A23187 was measured in RBL-1 cells by high-performance liquid chromatography. Honokiol inhibited the production of LTC4 and LTB4 stimulated by A23187 in RBL-1 cells. Honokiol did not inhibit either phospholipase A2 activity, measured by the release of 3H-arachidonic acid (AA), or LTC4 synthase and LTA4 hydrolase activities, measured with LTA4-free acid as substrate. The synthesis of LTC4 and LTB4 from AA in RBL-1 cell lysates in the presence of Ca2+ was inhibited by honokiol. These results indicate that honokiol blocks LT synthesis by inhibiting 5-lipoxygenase activity. Honokiol also inhibited immunoglobulin E-mediated production of these LTs in RBL-2H3 cells, which was measured by a specific radioimmunoassay (RIA). These results suggest that honokiol may exhibit antiallergic actions by inhibiting LT synthesis in immediate-type hyperreactivity.

Modification of the single unpaired sulfhydryl group of beta-lactoglobulin under high pressure and the role of intermolecular S-S exchange in the pressure denaturation [single SH of beta-lactoglobulin and pressure denaturation]

Chemical modification reactions of the unpaired sulfhydryl group of beta-lactoglobulin (LG) under high pressure and the role of this group in the pressure-induced denaturation were investigated. When LG was incubated at 400 MPa (pH 6.8) for 1 h, dimerization through intermolecular reaction of SH was observed. The generation of the covalently linked dimers were prevented by the presence of N-ethylmaleimide (NEM), an agent for SH-specific modification. The reactivity of the SH group of LG, which is buried inside in its native state, was increased by high pressure, as a result of its exposure to the protein surface accompanied by the pressure denaturation. The effect of NEM was also observed in the fluorescence change caused by high pressure, in both the intrinsic fluorescence of LG and the retinol fluorescence of the LG-retinol complex. The control showed an irreversible change at neutral pH, but it became mostly reversible in the presence of NEM. Compatible results were obtained by CD spectroscopy. Inter- and intramolecular reactions of the SH group are suggested to be main causes for the pressure-induced irreversible denaturation of LG.

An immunohistochemical study of HLA-DR and alpha 1-antichymotrypsin-positive cells in the pulp of human non-carious and carious teeth

The condition of the pulp tissue was classified into seven groups according to the progression of carious lesions from stages S0 (non-carious teeth) to S6 (exposed pulp). There was a small number of anti-HLA-DR antibody-positive cells in the pulp of the early carious teeth, and a markedly increased number at S5 and S6. The recruitment of a large number of anti-HLA-DR cells concomitant with a marked increase of other kinds of immunocompetent cells in the pulp of late-stage caries might indicate the occurrence of antigen presentation followed by both cell-mediated and humoral immune reactions. The number of anti-alpha 1-antichymotrypsin (ACT) antibody-positive macrophages showed a proportional increase with the development of caries, and these cells may be involved in protecting against the tissue damage caused by proteases released from inflammatory cells, as well as having a defensive role by phagocytosis of toxic micro-organisms and damaged tissue residues. Thus anti-HLA-DR and anti-ACT antibody-positive cells might participate in both an efficient immune system and a tissue-protective mechanism in the human dental pulp.

Pressure-induced change in proteins studied through chemical modifications

Pressure-induced change of two bovine proteins, alpha-lactalbumin (LA) and beta-lactoglobulin (LG), was investigated at neutral pH by means of fluorescence and CD spectroscopy. The rate and the extent of modification was considerably increased by applying high pressure during the dansylation reaction of LG, while those for LA were only moderately affected. This difference was accounted for by the structural deformation of these proteins under high pressure. The fluorescence spectrum of these proteins measured under elevated pressure, as well as their fluorescence and CD spectra after the pressure release, indicated different responses towards pressure. The structural change of LA was practically reversible up to 400 MPa, whereas that of LG lost reversibility at 150 MPa or lower. Fluorescent measurement of dansylated (prepared at atmospheric pressure) proteins, especially the energy transfer from the intrinsic Trp residue to the dansyl group, showed that the protein structure was deformed by pressure and that the energy transfer facility of the two proteins was differently affected by high pressure, probably reflecting the degree of compactness of their pressure-perturbed structures.

Relationship between the amount of propranolol permeating through the stratum corneum of guinea pig skin after application of propranolol adhesive patches and skin irritation

In the present study we evaluated the relationship between the cumulative amount of propranolol permeating through the stratum corneum and the formation of erythema, a skin irritation reaction, after transdermal application of adhesive patches containing propranolol to the skin of guinea pigs. The intensity of erythema was expressed in terms of a* values measured with a chromameter. The a* values increased in guinea pigs after application of the adhesive patches containing 0.4 mg/cm2 of propranolol to the skin. Since the adhesive patches showed good adhesion to the skin (propranolol content is less than the saturated concentration in the adhesive base) and the cumulative amount of propranolol permeating through the stratum corneum is small, the development of erythema was considered to be mainly due to physical factors such as peeling. Even in adhesive patches containing 0.8 mg/cm2 or 1.2 mg/cm2 of propranolol, a* values increased, although adhesion to the skin is low because of crystallization of propranolol in the adhesive base. On the other hand, in these two adhesive patches, the cumulative amount of propranolol permeating through the stratum corneum increased up to 24 h after application. These findings suggest that the skin irritation reaction is due to propranolol mainly absorbed transdermally, because there is a high correlation between the cumulative amount of propranolol permeating through the stratum corneum and the a* values (r = 0.928).

[Inhibitory effects of saiboku-to and compornent herbs on the production of peptide leukotrienes (LTs) and LTB4]

We investigated the effects of Saiboku-to, Syoseiryu-to and compornent herbs of these two Kampo-Medicines (Saiko, Hange, Bukuryo, Ogon, Koboku, Taiso, Ninjin, Kanzo, Soyo, Syokyo, Keihi, Gomisi, Saisin, Syakuyaku, Mao and Kankyo) on the production of peptide leukotrienes (LTs) and LTB4 in cultured rat basophilic leukemia (RBL)-1 cells. Cultured RBL-1 cells were stimulated with Ca ionophore, A23187, at 10(-5) M in the absence or presence of various concentrations of these substances, and the production of peptide LTs and LTB4 was measured by reversed phase-high performance liquid chromatography (RP-HPLC). The production of LTs was dose-dependently suppressed by the addition of Saibokuto. Saiboku-to (100 micrograms/ml) showed 35% and 30% inhibition on the production of peptide LTs and LTB4, respectively. These inhibitory actions of Saiboku-to on LT-synthesis were attributable to the effects of its component herbs, Ogon, Koboku and Kanzo. On the other hand, Syoseiryu-to showed no inhibitory action on LT-production. these results indicate that anti-allergic action of Saiboku-to is, at least in part, attributable to its inhibitory action on LT-synthesis.

Sulfated colominic acid: an antiviral agent that inhibits the human immunodeficiency virus type 1 in vitro

Colominic acid is a homopolymer of N-acetylneuraminic acid (NANA), which has an alpha-2,8 ketosidic linkage between its polymer units. In this study, colominic acids were sulfated under different conditions and their antiviral activities against human immunodeficiency virus type 1 (HIV-1) were examined. Sulfated colominic acids, containing 6-12% sulfur, blocked the expression of HIV-1 antigen in MT-4 cells or C8166 cells following exposure to MOLT-4/HTLV-IIIB or HIV-1[GUN-1]. The compounds inhibited syncytium formation upon co-cultivation of MOLT-4 cells (clone 8) with MOLT-4/HTLV-IIIB cells and abolished the production of HIV-1 p24 antigen in culture medium of peripheral blood lymphocytes (PBLs). HIV-1 reverse transcriptase (RT) activity was not directly affected by the drugs. The compounds did not prolong activated partial thromboplastin time (APTT) at 10 and 1.0 microgram/ml, suggesting that they may not have appreciable side effects in vivo. These agents were still able to block the expression of HIV-1 antigen even when the cells were infected with HIV-1 in RPMI-1640 medium containing high percentages of fetal calf serum (FCS). These properties may be therapeutically advantageous if these compounds were considered for possible clinical use.

[Drug-resistance patterns of clinical isolates of Pseudomonas aeruginosa in regard to their lipopolysaccharide-chain sizes]

Pseudomonas aeruginosa strains isolated from patients with different types of the infections each consisted of LPSs different in chain sizes. The drug-susceptibility patterns of these strains of P. aeruginosa were investigated to clarify the relationship between the LPS-compositions and susceptibility to some kinds of anti-pseudomonal drugs. The susceptibilities of nineteen strains (seven long-LPS strains, four short-LPS strains and eight LPS-deficient strains) to piperacillin, ceftazidime, gentamicin, norfloxacin and polymyxin-B were determined and these strains were classified into six types (Types I-VI) according to their drug-resistance patterns. Six of the eight LPS-deficient strains were found to be highly resistant to gentamicin alone (Type IV). Four of the seven strains with the long-LPS and one strain with the short-LPS were resistant to three drugs such as piperacillin, ceftazidime and norfloxacin, and classified into Type I. These results indicated that the major part of the LPS-deficient strains and the considerable part of the long-chain LPS strains of P. aeruginosa tested had each characteristic profile in the drug resistance. The outer membrane proteins of thirteen strains, consisting of different types of LPS compositions, were analyzed by SDS-PAGE. The strains belonging to the same types of the drug-resistance patterns were found to have similar OMP-profiles, although a few exceptions were found. beta-lactamase and gentamicin-inactivating activities were determined for piperacillin-resistant and gentamicin-resistant strains, respectively. Of the piperacillin-resistant strains tested, the activity of beta-lactamase was high in one (No. 8) only, low in four and not found in four. The results showed that degrees of resistance of P. aeruginosa strains tested to piperacillin did not correlate to their producibility of beta-lactamase except one strain. Of the nine gentamicin-resistant strains tested, the gentamicin inactivating activity was high in one (No. 30) only, moderate in six and low in two. These results suggested that the significant levels of piperacillin- or gentamicin-resistance of P. aeruginosa isolated tested might be expressed each due to their decreased abilities for drug-permeabilities in addition to drug-inactivating activities such as beta-lactamase or gentamicin-modifying enzyme. In the case of some resistant strains, the resistance to piperacillin or gentamicin was not explained by the results of the present study. Therefore, we must investigate the possibility that other mechanisms participate in the resistance of these strains.

Beneficial effect of amiloride, A Na(+)-H+ exchange blocker, in a murine model of dilated cardiomyopathy

We investigated the effect of amiloride, a Na(+)-H+ exchange blocker, on ventricular hypertrophy in a murine model of dilated cardiomyopathy (DCM). Mice with DCM were given orally amiloride for 60 days. The ratio of heart weight to body weight and left ventricular cavity dimension were significantly smaller in both amiloride groups than those in furosemide and control (untreated DCM) groups (p < 0.05). The fiber diameter was significantly smaller in amiloride groups than that in furosemide group (p < 0.01). Plasma and cardiac angiotensin II (AII) levels were decreased in amiloride-treated groups compared with those in furosemide or control group (p < 0.05). Our findings suggest that amiloride prevents the development of myocardial hypertrophy and left ventricular dilatation in DCM in association with a reduction of AII.

Inspiratory coactivation of the genioglossus enlarges retroglossal space in laryngectomized humans

To investigate the relationship between the electrical activity of the genioglossus (GG-EMG) and associated tongue movement, seven laryngectomized subjects breathing through a tracheal stoma (without pressure or flow change in the upper airway) were studied in the supine position. Tongue movement, with the use of lateral fluoroscopy, and GG-EMG expressed as a percentage of maximum voluntary genioglossal activation were monitored simultaneously during 1) spontaneous inspiration (SI), 2) resistive loaded inspiration (LI), and 3) rapid inspiration (RI). Tongue position during each maneuver was compared with its position during spontaneous expiration. Peak GG-EMG during the three maneuvers was significantly different from each other (SI: 5.4 +/- 1.6, LI: 11.9 +/- 1.8, and RI: 51.6 +/- 9.4 (SE) %, respectively). Associated forward movement of the posterior aspect of the tongue was minimum during SI; however, significant movement was observed during LI, and this was increased during RI. Significant covariance existed between peak GG-EMG and this movement. Genioglossal coactivation with inspiration enlarges the glossopharyngeal airway, particularly in its caudal part. In subjects with intact upper airways, this activation may protect or enhance upper airway patency in an effort-dependent manner.

Inhibition of leukotriene synthesis by azelastine

BACKGROUND

Azelastine, oxatomide, and ketotifen are used for patients with allergic diseases. These drugs inhibit the release of chemical mediators including the leukotrienes; however, the mechanism involved is unclear.

OBJECTIVE

To clarify the mechanism of inhibition, we investigated the effects of three drugs on the function of phospholipase A2, 5-lipoxygenase, leukotriene C4 synthase, and leukotriene A4 hydrolase, which are all catabolic enzymes involved in synthesizing leukotriene C4 and leukotriene B4 in rat basophilic leukemia (RBL)-1 cells.

METHODS AND RESULTS

The production of leukotriene C4 and leukotriene B4 was measured by high performance liquid chromatography (HPLC). All three drugs inhibited the production of leukotriene C4 and leukotriene B4 when cells were stimulated with A23187. All three drugs also inhibited the A23187-stimulated release of 3H-arachidonic acid from membrane phospholipids. Azelastine inhibited the production of leukotriene C4, but not leukotriene B4, when either arachidonic acid or leukotriene A4 free acid was used as the substrate in our cell free system. Oxatomide and ketotifen did not inhibit the synthesis of either leukotriene C4 or leukotriene B4 in the same cell free study.

CONCLUSION

Results indicated that oxatomide and ketotifen inhibit the production of leukotriene C4 and leukotriene B4 by inhibiting phospholipase A2 activity, whereas, azelastine inhibits the leukotriene C4 production by inhibiting phospholipase A2 and leukotriene C4 synthase.

Orientation dependence in homologous recombination

Homologous recombination was investigated in Escherichia coli with two plasmids, each carrying the homologous region (two defective neo genes, one with an amino-end deletion and the other with a carboxyl-end deletion) in either direct or inverted orientation. Recombination efficiency was measured in recBC sbcBC and recBC sbcA strains in three ways. First, we measured the frequency of cells carrying neo+ recombinant plasmids in stationary phase. Recombination between direct repeats was much more frequent than between inverted repeats in the recBC sbcBC strain but was equally frequent in the two substrates in the recBC sbcA strain. Second, the fluctuation test was used to exclude bias by a rate difference between the recombinant and parental plasmids and led to the same conclusion. Third, direct selection for recombinants just after transformation with or without substrate double-strand breaks yielded essentially the same results. Double-strand breaks elevated recombination in both the strains and in both substrates. These results are consistent with our previous findings that the major route of recombination in recBC sbcBC strains generates only one recombinant DNA from two DNAs and in recBC sbcA strains generates two recombinant DNAs from two DNAs.