A magnetic topological semimetal Sr1-yMn1-zSb2 (y, z < 0.1)

Weyl (WSMs) evolve from Dirac semimetals in the presence of broken time-reversal symmetry (TRS) or space-inversion symmetry. The WSM phases in TaAs-class materials and photonic crystals are due to the loss of space-inversion symmetry. For TRS-breaking WSMs, despite numerous theoretical and experimental efforts, few examples have been reported. In this Article, we report a new type of magnetic semimetal Sr_1-yMn_1-zSb₂ (y, z < 0.1) with nearly massless relativistic fermion behaviour (m^∗ =  0.04 - 0.05m₀, where m₀ is the free-electron mass). This material exhibits a ferromagnetic order for 304 K  <  T  <  565 K, but a canted antiferromagnetic order with a ferromagnetic component for T  <  304 K. The combination of relativistic fermion behaviour and ferromagnetism in Sr_1-yMn_1-zSb₂ offers a rare opportunity to investigate the interplay between relativistic fermions and spontaneous TRS breaking.

Apoptosis induction in duck tissues during duck hepatitis A virus type 1 infection

To investigate the role of apoptosis in duck viral hepatitis pathogenesis, 4- and 21-d-old ducks were inoculated with duck hepatitis A virus serotype 1 and killed at 2, 6, 12, 24, and 48 h postinfection. TdT-mediated dUTP nick-end labeling was used to detect apoptosis cells. Expression profiles of apoptosis-related genes including caspase-3, -8, -9, and Bcl-2 in spleen, bursa of Fabricius, liver, and the quantity of virus in blood were examined using real-time PCR. The TdT-mediated dUTP nick-end labeling analysis indicated there was a significant difference of apoptotic cells between treatments and controls. The same difference also appeared in virus amount variation in blood during infection. Gene expression analysis revealed that the apoptosis-related gene expression profile was different in the 2 groups, and also different between various organs. This study suggested that apoptosis may play an important role in duck hepatitis A virus serotype 1 infection, and apoptosis suppression might facilitate virus multiplication, resulting in the highest virus concentration in the host.

Mössbauer study of superconducting NdFeAsO(0.88)F(0.12) and its parent compound NdFeAsO

(57)Fe Mössbauer spectroscopy has been used to investigate the magnetic order of non-superconducting NdFeAsO (T(N) = 140 K) and superconducting NdFeAsO(0.88)F(0.12) (T(c) = 45 K). A magnetic hyperfine field B(hf) was observed at the (57)Fe nucleus below T(N)∼140 K for NdFeAsO. Below ∼2 K an increase of B(hf) relative to the saturation value was attributed to the transferred B(hf) at the Fe site resulting from the collinear antiferromagnetic (AF) spin structure of the Nd moments. The analysis of the spectra is consistent with a commensurate AF order of Fe spins. No  B(hf) is observed in superconducting NdFeAsO(0.88)F(0.12) down to 1.5 K.

Role of Interleukin-6 in the Pathogenesis of an Avian Model of Staphylococcus aureus Arthritis

To evaluate the role of interleukin-6 (IL-6) in arthritis induced by Staphylococcus aureus, a chicken model was developed for study. A total of 120 healthy broilers (8 wk old) were randomly divided into 4 groups. Two groups were injected with 0.35 mL of Staph. aureus (7.1x10(9) cfu/mL) into the right hock joints and the other 2 were injected with 0.35 mL of sterile saline into the same joints. One group of each of the 2 treatment groups was fed levofloxacin at a dose of 5 mg/kg of BW on the third day postinoculation for 4 successive days. Chicken blood samples were obtained on d 0, 1, 4, 7, 14, 21, 28, and 35 postinoculation. Chicken IL-6 (chIL-6) activities and concentrations in serum were quantified by B9 bioassay and human IL-6 ELISA, respectively. The results showed that chIL-6 activities and concentrations were reduced (P<0.05) in the serum of infected broilers treated with levofloxacin compared with birds injected only with Staph. aureus. Levofloxacin treatment had no effect on IL-6 activities and concentrations in uninfected broilers. There was a strong correlation (r=0.91) between serum chIL-6 activities by the B9 bioassay and serum IL-6 concentrations determined by the human IL-6 ELISA. We concluded that chIL-6 is involved in the progression of chicken arthritis induced by Staph. aureus, and that it contributes to disease incidence and mortality.

[Inhibitory effects of benzoisoselenothiazolidone sulfonamide derivatives on cyclooxygenase]

AIM

To study the inhibitory effects of benzisoselenothiazolidone sulfonamide derivatives on cyclooxygenase.

METHODS

6-Keto-PGF1 alpha and PGE2 were assayed by radioimmunoassay (RIA) method; mRNA expression of COX-1 and COX-2 were assayed by reverse transcription-polymerase chain reaction (RT-PCR) method.

RESULTS

Compound A [N-4-(4-methoxyphenyl-aminosulfonyl)-benziososelenothiazolidone] and B [N-4-(4-fluorophenyl-aminosulfonyl)-benzoisoselenothiazolidone] were two benzoisoselenothiazolidone sulfonamide derivatives, which can inhibit COX activity with IC50 of 1.5 x 10(-8) mol.L-1 and 5.0 x 10(-8) mol.L-1 for COX-2, as well as IC50 of 1.5 x 10(-5) mol.L-1 and 2.8 x 10(-5) mol.L-1 for COX-1. The ratio of IC50 COX-1/IC50 COX-2 of compound A and B are 1,000 and 560, respectively. They both can inhibit COX-2 mRNA expression in cultured rat peritoneal macrophages stimulated with LPS (1 microgram.mL-1), and have no effect on COX-1 mRNA expressions.

CONCLUSION

Compound A and B, two benzoisoselenothiazolidone sulfonamide derivatives, both are selective inhibitory agents of COX-2, and possess inhibitory effects on 5-lipoxygenase and cyclooxygenase.

Anti-inflammatory tetramers of resveratrol from the roots of Vitis amurensis and the conformations of the seven-membered ring in some oligostilbenes

Five resveratrol tetramers, amurensins I-M, were isolated from the roots of Vitis amurensis (Rupr.), together with five known resveratrol tetramers, (+)-hopeaphenol, isohopeaphenol, vitisin A, (+)-vitisifuran A, and heyneanol A. Their structures and stereochemistry were determined by chemical and spectroscopic methods, especially by use of 2D NMR analysis. Some of them had an ampelopsin A or a balanocarpol unit, in which the conformations of the seven-membered carbon ring were described for the first time. The anti-inflammatory activities of the tetramers were also tested. Among them, (+)-hopeaphenol, isohopeaphenol, vitisin A, (+)-vitisifuran A and heyneanol A showed potent inhibition on the biosynthesis of leukotriene B4 (LTB4), and amurensins I and L showed strong antagonism of the histamine acceptor.

[Inhibitory effects of hydrocortisone on human polymorphonuclear leukocyte adhesion to human synovial cell]

AIM

To investigate the inhibitory effects of hydrocortisone on human polymorphonuclear leukocyte (PMN) adhesion to human synovial cell (HSC), and to explore its mechanism.

METHODS

MTT colorimetry was used to determine the adhesion effect of PMN to HSC. Cell-ELISA and RT-PCR methods were used to determine the expression of adhesion molecular ICAM-1 and VCAM-1. EMSA method was also used to observe the activity of nucleus transcription factor-kappa B (NF-kappa B).

RESULTS

Hydrocortisone inhibited TNF-alpha (50 U.mL-1 for 12 hours) and IL-1 beta (50 U.mL-1 for 12 hours)-induced adhesion of PMN to HSC (IC50 2.05 x 10(-6) mol.L-1 and 2.13 x 10(-7) mol.L-1, respectively) in a concentration-dependent manner. Adhesion molecular VCAM-1 and ICAM-1 protein and mRNA (rather than ICAM-1) expression in HSC induced by TNF-alpha (50 U.mL-1) were inhibited significantly by hydrocortisone at 1 x 10(-6)-10(-5) mol.L-1. The activity of NF-kappa B was also extensively inhibited by hydrocortisone at 1 x 10(-6)-10(-5) mol.L-1.

CONCLUSION

Hydrocortisone inhibited TNF-alpha-stimulated PMN-HSC adhesion, and expression of VCAM-1 by suppressing the activity of NF-kappa B.

[Inhibitory effects of isorhapotigenin on IL-8 production and mRNA expression induced with TNF alpha in normal human synovial cells]

AIM

To study the effects of isorhapotigenin (Iso) on interleukin-8 (IL-8) production and mRNA expression in normal human synovial cells (HSC) induced with TNF alpha.

METHODS

IL-8 were assayed with RIA method. The mRNA expression of IL-8 was detected by RT-PCR method.

RESULTS

It was shown that TNF alpha at concentrations of 0.05 to 0.5 U.mL-1 for 24 h significantly increased IL-8 production. The expression of IL-8 mRNA was also promoted by TNF alpha (0.25 U.mL-1) for 6 h. Iso at the concentrations of 1 x 10(-6) mol.L-1 to 1 x 10(-5) mol.L-1 showed inhibitory effects on IL-8 production induced with TNF alpha (0.25 U.mL-1). The further study indicated that Iso at the concentrations of 1 x 10(-6) mol.L-1 to 1 x 10(-5) mol.L-1 inhibited IL-8 mRNA expression in HSC induced with TNF alpha (0.25 U.mL-1).

CONCLUSION

TNF alpha promoted IL-8 production and mRNA expression in HSC. Iso inhibited IL-8 production and mRNA expression induced by TNF alpha (0.25 U.mL-1). This might be one of the anti-inflammatory mechanisms of Iso.

[Inhibitory effects of indomethacin and meloxicam on NF-kappa B in mouse peritoneal macrophages]

AIM

To study the inhibitory effects of indomethacin and meloxicam on NF-kappa B from lipopolysaccharide (LPS) stimulated peritoneal macrophages of mice.

METHODS

NF-kappa B was measured with the method of electrophoretic mobility shift assay (EMSA).

RESULTS

After induction by LPS at the concentrations of 1 and 3 micrograms.mL-1, the NF-kappa B content of the mouse peritoneal macrophages increased markedly. Indomethacin and meloxicam, at the concentrations of 10(-7)-10(-5) mol.L-1, decreased the activation of NF-kappa B at the concentrations of 1 and 3 micrograms.mL-1 in activated mouse peritoneal macrophages induced with LPS at the concentrations of 1 and 3 micrograms.mL-1.

CONCLUSION

The inhibitory effects of indomethacin and meloxicam on NF-kappa B activation may be one of their mechanisms of antiinflammatory actions.

[Effect of stilbene polymer (Gn-3) on experimental liver injuries in mice]

AIM

To study the protective effect of Gn-3 (a stilbene polymer isolated from Gnetum parvifolium) against liver injury induced by CCl4, N-acetyl-p-aminophenol (APAP) and Bacillus Calmette-Guerin (BCG) plus bacterial lipopolysaccharide (LPS) in mice.

METHODS

The experimental model of liver injury were induced by 0.1% CCl4 i.p. (10 mL.kg-1.d-1 for 3d), APAP i.p. (150 mg.kg-1) or BCG (5 mg) plus LPS (7.5 micrograms) in mice. The levels of ALT in serum, MDA and GSH in liver tissues were detected. The histopathologic changes were observed by light microscope.

RESULTS

Gn-3 was shown to markedly reduce the elevated serum ALT levels, liver tissue MDA and improve the histopathological changes in all the three experimental liver injury models. No effect of Gn-3 was observed on the liver GSH level in liver injury mice.

CONCLUSION

Gn-3 was found to inhibit the development of liver injury caused by CCl4, APAP, or BCG plus LPS. This means that Gn-3 has liver protective effects.

[Effects of ginkgolide B on arachidonic acid metabolizing enzymes and level of intracellular calcium in rat polymorphonuclear leukocytes]

AIM

To investigate the effects of ginkgolide B on arachidonic acid (AA) metabolizing enzymes and the level of intracellular calcium in rat polymorphonuclear leukocytes.

METHODS

Intracellular free calcium was quantitated by Fura-2 fluorescence technique. Phospholipase A2 (PLA2) activity was determined by incorporating 3H-arachidonic acid in leukocytes. 5-Lipoxygenase (5-LO) activity was evaluated by RP-HPLC.

RESULTS

In comparison with control, ginkgolide B at final concentration of 0.1-10 mumol.L-1 inhibited A23187 induced AA release by 10.9%-22.2%; at final concentration of 0.1-50 mumol.L-1, ginkgolide B inhibited LTB4 and 5-HETE synthesis stimulated by PAF by 29.4%-88.8% and 26.2%-89.3% respectively. At the final concentration of 0.1-100 mumol.L-1, ginkgolide B decreased the rise of intracellular calcium level induced by pletelet activating factor (PAF) and N-formyl-methionine-leucine-phenglalanine (fMLP) by 13.9%-51.4% and 2.2%-36.6%, respectively.

CONCLUSION

Ginkgolide B was found to significantly inhibit PLA2 and 5-LO activities, as well as the increase of the intracellular calcium induced by PAF.

[Effects of musk glucoprotein on the function of rat polymorphonuclear leukocytes activated by IL-8 in vitro]

OBJECTIVE

To investigate the effects of musk-1, a glucoprotein component isolated from the water extract of musk, on some functions of rat polymorphonuclear leukocytes activated by IL-8 in vitro.

METHOD

An in vitro incubation system was used. Superoxide anion production was determined by cytochrome C reduction. beta-glucuronidase and lysozyme release was quantitated by enzyme reactions in which phenolph-thaleinglucuronic acid and Micrococcus Lysodeikticus were as the substrates, respectively.

RESULTS

In comparison with control, musk-1 at concentration 1-100 micrograms.ml-1 can increase superoxide anion production by 91.7%-291%, and decrease beta-glucuronidase and lysozyme release by 2.2%-58.1% and 3.9%-39.8%, respectively.

CONCLUSION

Inhibition of lysosomel enzyme release might be considered as one of mechanisms of antiinflammatory action of musk.

[Effects of musk glucoprotein on PAF production and cytosolic Ca2+ level in rat polymorphonuclear leukocytes in vitro]

OBJECTIVE

To investigate the effects of Musk glucoprotein on platelet activating factor (PAF) production and the concentration of cytosolic free Ca2+ in polymorphonuclear leukocytes of rat.

METHODS

An in vitro incubation system was used, production of PAF and activity of acetyl transferase were measured by isotope incorporation, the concentration of cytosolic free Ca2+ was quantitated using the fluorescent Ca2+ indicator Fura-2.

RESULTS

Musk-1 at concentration of 1-100 micrograms.ml-1 can significantly inhibit production of PAF, activity of acetyl transferase and the increase of cytosolic Ca2+ concentration in polymorphonuclear leukocytes of rat.

CONCLUSION

Part of mechanisms underlying antiinflammatory action of Musk-1 is through inhibiting the synthesis of PAF and the increase of cytosolic Ca2+ level.

[Effects of baicalin on liver microsomal cytochrome P450 system]

AIM

To investigate the effect of baicalin on liver microsomal cytochrome P450 system and the mechanism of liver protective action of baicalin.

METHODS

Liver microsomal cytochrome P450, b5, aminopyrin N-demethylase (ADM), 7-ethoxycoumarin O-deethylase (ECD) and benzopyrene hydroxylase (AHH) activity were quantitated by UV chromatography. Activities of six cytochrome P450 isoforms were assayed with Western Blotting.

RESULTS

Baicalin increased liver microsomal cytochrome. P450 level and ADM, ECD and AHH activity significantly. The three P450 isoforms, 1A1, 2B1 and 2C11, were also induced selectively by baicalin, but the b5 level, 3A2, 2D1 and 2E1 were not induced.

CONCLUSION

Baicalin increases liver microsomal cytochrome P450 level and induces selectively 1A1, 2B1 and 2C11 of P450 isoforms in mice.

Regulation of murine interleukin-10 production by dehydroepiandrosterone

Dehydroepiandrosterone (DHEA), one of the predominant androgens secreted by the adrenal cortex, is a potential immunologic regulator. In this report, the effect of DHEA on interleukin-10 (IL-10) production was studied in vivo. Mice were injected s.c. with DHEA or DHEA-sulfate (DHEAS) ranging from 50 microg to 500 microg/g body weight. The serum was collected, and the spleen cells were isolated 48 h after treatment. Results indicate that treatment with DHEA or DHEAS significantly increases the serum level of IL-10. The spleen cells isolated from the DHEA-treated or DHEAS-treated mice also showed an increase in IL-10 secretion and mRNA expression after the cells were activated by concanavalin A (ConA). The maximal dose of DHEA for inducing IL-10 production was 250 microg/g body weight. As IL-10 is a potent differentiation factor of B lymphocytes, the possible role of DHEA in regulation of immunoglobulin (Ig) production was studied in vivo. Results indicated a significant increase in both serum level of Ig (IgG, IgM, IgA) and Ig secretion by spleen cells after the mice were treated with DHEA or DHEAS. Mice injected with both DHEA (250 microg/g body weight) and anti-IL-10 antibody (0.5 mg/g body weight) showed a significantly reduced DHEA-mediated increase in Ig production. Thus, DHEA might affect the function of B lymphocytes via stimulating IL-10 production.

Inhibitory effect of resveratrol on interleukin 6 release by stimulated peritoneal macrophages of mice

In the present investigation, interleukin 6 (IL-6) activity in the supernatant of cultured mouse peritoneal macrophages was monitored using a sensitive bioassay involving the IL-6-dependent murine hybridoma B9 cell line. The effects of resveratrol on Il-6 release by mouse peritoneal macrophages stimulated with calcium ionophore A23187 and fMLP were explored. Resveratrol, at a concentration range from 5 x 10(-6) to 4 x 10(-5) mol.l-1, was found to dose-dependently inhibit IL-6 release by cultured macrophages induced by A23187 and fMLP, and showed no direct cytotoxic effect, but induced proliferation of cultured mouse thymus cells. Resveratrol, at a concentration range from 10(-8) to 10(-5) mol.l-1, was shown to dose-dependently inhibit calcium ion influx into the cells with the stimulation of fMLP (10(-6) mol.l-1). These results suggest that the blocking of calcium ion influx into cells by reveratrol is one of the possible mechanisms of the IL-6 biosynthesis inhibitory action of resveratrol.

[Studies on the characteristics of leukotriene B4 receptor with radio-ligand binding assay]

Leukotriene B4 (LTB4), one of the metabolites of arachidonic acid via 5-lipoxygenase (5-LO), plays important role in some inflammatory diseases as one of the most potent chemotaxis factor. A radio-ligand binding assay was set up and the characteristics of LTB4 receptor on guinea-pig splenocytes membrane were studied. At 25 degrees C, the Kd was found to be 1.55 x 10(-9) mol.L-1 and the Bmax was 2.59 x 10(-13) mol.mg-1 protein. The assay established was evaluated by nordihydroguaiaretic acid (NDGA) as positive control.

[Structure-activity relationship studies of chalcones as SRS-A receptor antagonists]

A simple, reliable and highly sensitive bioassay with sensitized longitudinal strips of guinea pig ileum was used for screening the receptor antagonists of slow reacting substance of anaphylaxis (SRS-A). The SRS-A receptor antagonistic activities of 17 chalcones were studied. Most compounds in these chalcones were found to have SRS-A receptor antagonistic action at the concentration of 10(-4) mol.L-1. Among them, compounds 5, 13 and 17 were highly effective with IC50s of 7.5 x 10(-6), 7.5 x 10(-6) and 6.8 x 10(-5) mol.L-1, respectively. Under the same conditions, the IC50 of FPL 55712, a known leukotriene D4 receptor antagonist, was shown to be 3 x 10(-4) mol.L-1. It would appear that compounds 5, 13 and 17 were 40, 40 and 4.4 times more potent, respectively, than FPL 55712. From analysis of structure-activity relationship of chalcones, these results suggest that the following factors may be important for an active antagonist of SRS-A receptors: (a) There is a system of pi, pi conjugation in the molecule; (b) The ester group in the B ring of chalcones is more favorable than the carboxyl group; (c) Antagonism for meta- or para-substituted derivatives of carboxyl or ester group in the B ring are more potent than ortho-substituted compounds; (d) The length of carbon chain of alkyl group in the A ring of chalcones is more effective for 1, 4 or 6 carbon atoms than for 10 or 14 carbon atoms.

Diagnosis and treatment of adrenal tumours: a review of 35 years' experience

OBJECTIVE

To review and analyse clinical data on the diagnosis and management of patients with adrenal masses.

PATIENTS AND METHODS

Patients admitted with adrenal masses between 1960 and 1995 were reviewed. The series comprised 116 males (mean age 41.4 years, SD 10.5, range 3-77) and 95 females (mean 36.9 years, SD 11.6, range 1-62); eight patients were < 14 years old and the overall mean (SD) age was 39.4 (12.8) years. The diagnosis was based on symptoms, signs, hormone levels and imaging studies. All tumours were confirmed by surgery, and pathology and results of analysis assessed statistically.

RESULTS

Over the last 35 years, the incidence of adrenal tumours was 1.7% of all patients admitted with genitourological diseases or 9.7% of patients with genitourinary tumours at our institution. The prevalence of adrenal tumours in males and females was similar but Cushing's syndrome was 3.1 times more frequent in females than in males and phaeochromocytoma 1.9 times more frequent in males than females. Most patients with adrenal tumour were aged 30-50 years. Of 211 adrenal tumours, 151 (72%) were functional, with a prevalence of benign tumour, and 60 (28%) were nonfunctional, with 35% malignant. There were 78 'incidentalomas' which included 18 functional tumours. Overall, 210 tumours were removed and one was explored. Correlation analysis between tumour size and character or hormone levels showed that size was significantly positively correlated with tumour character (r = 0.4010, P < 0.001), but there was no relationship between tumour size and hormonal levels. The postoperative complication rate was 3.3% and the mortality 0.5%.

CONCLUSIONS

Based on this analysis we recommend that computed tomography is the first method used to define and localize the adrenal masses, that hormone levels should be determined in symptomatic or asymptomatic patients with adrenal masses, and that functional adrenal tumours and solid incidentalomas of any size should be removed surgically.

Benign cystic teratoma of unilateral fallopian tube associated with intrauterine pregnancy: a case report

Primary teratomas of the fallopian tube are extremely uncommon. To date, only about 50 cases have been reported in the literature. Six of them are reported to have been in conjunction with tubal ectopic pregnancies. Herein we present the first case of benign cystic teratoma of the unilateral fallopian tube associated with an intrauterine term pregnancy, reported in Taiwan.

[Production and secretion of interleukin 6 from stimulated peritoneal macrophages of the mouse]

In this paper, a bioassay method involving the interleukin 6 dependent murine hybridoma B9 cell line was used to detect the level of released and cell-associated interleukin 6 in resident peritoneal macrophages from the mouse. The phorbol ester, phorbol 12-myristate 13-acetate (PMA), the calcium ionophores A23187, the chemotactic peptide fMLP and lipopolysaccharide(LPS) were introduced in these experiments as stimulators. PMA, A23187 and fMLP were shown to induce a dose-dependent increase of both released and cell-associated interleukin 6, whereas, LPS caused increase of interleukin 6 activity in supernatants of cultured peritoneal macrophages of the mouse. The effects of PMA and A23187 suggested that the pathway of PKC and calcium is involved in the production and secretion of interleukin 6. The effects of fMLP and LPS provided evidence that they participated in the process of inflammation. The difference between LPS and the other three stimulators in cell-associated interleukin 6 activity might suggest a different mechanism of actions of generation of interleukin 6.

[Determination of puerarin in plasma by high performance liquid chromatography]

A high performance liquid chromatography with fluorescence detection has been developed for determination of puerarin in plasma using a column of YWG-C16 (10 microns) and mobile phase of methanol (450 ml)-water (522.5 ml)-0.1 mol.L-1 phosphate buffer (pH 7.4, 27.5 ml). The preparation of samples was as follows: Transfer 0.1 ml of plasma into a 1 ml stoppered glass tube containing daidzein as internal standard, add 0.4 ml of absolute alcohol to deproteinize the plasma, vortex for 2 min, centrifuge for 15 min at 2800 r.min-1 and inject 20 microliters of the supernatant into the HPLC column. Linear calibration curve was obtained by plotting concentration vs peak height ratio over the range 0.03-12.00 micrograms.ml-1 with a correlation coefficient of 0.999. The average recovery of puerarin was 95.3% and the average RSD was 4.8%. The minimum detectable quantity of puerarin was 0.04 ng, equivalent to 10 ng.ml-1 plasma. This method is highly sensitive, specific, simple and rapid. The plasma concentration-time course of puerarin given i.v. 2.25 mg.kg-1 to two dogs determined by this method was found to fit a two-compartments open model with T1/2 alpha of 6.0 min and T1/2 beta of 57.4 min.

[Modulation of potassium channel by arachidonic acid]

Arachidonic acid is an important modulator for the inflammatory process. It can directly or indirectly regulate potassium channels which exist widely in the membrane of various types of cells. The direct modulation changes the conformation of potassium channel protein by the interaction between arachidonic acid and the protein, or through the interference with cell membranes around channels. The indirect influence of arachidonic acid upon channels results from its metabolites caused by cylcooxygenase and lipooxygenase, protein kinase C, and [Ca2+]i. All these aspects provide new potential targets for pharmacological investigations.

[Effect of tremulacin on actions of SRS-A and histamine]

The effect of tremulacin (TRC) extracted from Mao Bai Yang (Folia Populus tomentosa Carr) on actions of SRS-A and histamine were investigated by using isolated guinea pig ileum and spectrofluorometric assay. TRC was found to inhibit the contraction of isolated guinea pig ileum induced by histamine and SRS-A, in a dose-dependent manner with IC50 of 1.78 x 10(-4) mol.L-1 and 2.51 x 10(-4) mol.L-1, respectively. TRC at the dose of 10(-4) mol.L-1 inhibited SRS-A release from sensitized isolated guinea pig lung. While at the dose of 10(-5) mol.L-1 inhibited histamine release from the peritoneal mast cells in sensitized rats. These results indicate that inhibition of the release of histamine and SRS-A may play an important role in the mechanism of antiinflammatory actions of TRC.

Antiinflammatory effects of Tremulacin, a Salicin-related substance isolated from Populus tomentosa Carr. leaves

Tremulacin was shown to inhibit carrageenan-induced paw edema in rats and croton oil-induced ear edema in mice. It was also found to inhibit peritoneal leucocyte migration in rats and acetic acid-induced writhing responses in mice. Experiments with isolated longitudinal muscle strips of sensitized guinea pig ileum showed that tremulacin decreased the biosynthesis of Slow Reaction Substance of Anaphylaxis. Tremulacin exerted inhibitory effects on leukotriene B4 biosynthesis in intrapleural leucocytes. These results suggest that the mechanism of antiinflammatory actions of tremulacin is relevant to inhibition of 5-lipoxygenase activity. This is quite different from non-steroid antiinflammatory drugs, such as aspirin, which inhibits prostaglandin synthesis and being a cyclooxygenase inhibitor.

The role of cyclic AMP in chemoreception in the rabbit carotid body

The present study identified physiological factors which influence the generation (and degradation) of cyclic AMP (cAMP) in the arterial chemoreceptor tissue of the mammalian carotid body. Experiments established a 3-way correlation between cAMP generation, neurotransmitter release from chemoreceptor cells, and carotid sinus nerve (CSN) activity. Incubation of carotid bodies in vitro for 10 min in media equilibrated with different low O2 ('hypoxic') gas mixtures (5% O2 or 10% O2, balance N2) elevated basal cAMP levels (100% O2 media) in proportion to the stimulus intensity. Similar experiments using nodose sensory ganglia showed that low O2 stimulation did not alter cAMP levels in this non-chemosensory tissue. However, the adenylate cyclase (AC) activator, forskolin (10 microM), evoked large increases in the cyclic nucleotide content in both carotid bodies and nodose ganglia. After chronic (10 days) CSN denervation or sympathectomy, the basal levels of cAMP in the carotid body were elevated; the cAMP response to low O2 media (stimulus minus control) was increased after CSN denervation but remained unaltered after sympathectomy. The effects of zero Ca2+ media on cAMP generation was examined in order to assess whether feedback from released neurotransmitters acting on known (presynaptic) type I cell receptors could have contributed to the observed changes in cAMP. Basal levels of cAMP were increased 2.8-fold, and the response to hypoxic stimulation was elevated 5-fold, in the absence of extracellular Ca2+. Forskolin (10 microM) did not alter basal release of [3H]-catecholamines ([3H]CA; synthesized from [3H]tyrosine), or resting CSN discharge; however, stimulus-evoked [3H]CA release and CSN discharge were potentiated in the presence of forskolin.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of hypoxia on cyclic nucleotide formation in rabbit carotid body in vitro

The present experiments measured cAMP and cGMP in the arterial chemosensory tissue of the rabbit carotid body exposed for 10 min in vitro to normoxic or hypoxic conditions, or to specific activators of adenylate cyclase (forskolin) and guanylate cyclase (sodium nitroprusside). The enzyme activators elevated the basal levels of cAMP (48 x) and cGMP (3.7 x), respectively. Hypoxic media increased cAMP in the carotid body by 3.6-fold, but the levels of cGMP were reduced by 33% in media equilibrated with low O2. The data are consistent with the notion that cyclic nucleotides are involved in the transduction of natural stimuli and/or the neurotransmitter feedback modulation of chemosensory type I cells.