白藜芦醇对哇巴因所致豚鼠乳头状肌迟后去极化及触发活动的效应

研究旨在应用标准玻璃微电极技术,观察白藜芦醇对哇巴因所引起的离体豚鼠乳头状肌迟后去极化(delayed after depolarization,DAD)及触发活动(triggered activity,TA)的效应。结果显示：(1)预先给予白藜芦醇(30、60、120μmol／L)可剂量依赖性地抑制哇巴因所引起的乳头状肌DAD及TA;(2)预先应用L型钙通道开放剂Bay K8644(0．25μmol／L),可取消白藜芦醇的上述效应;(3)预先应用一氧化氮合酶抑制剂L-NAME(1mmol／L),对白藜芦醇的上述效应无影响;(4)单独应用17β-雌二醇(E2,5μmol／1．0或白藜芦醇(30μmol／L)对DAD及TA无明显影响,而联合应用相同剂量的E2和白藜芦醇则对DAD及TA产生明显的抑制效应;(5)预先应用雌激素受体拮抗剂他莫昔芬(10μmol／L)不能取消白藜芦醇对DAD及TA的抑制作用。以上结果表明,白藜芦醇具有抑制乳头状肌DAD及TA的作用,这一效应可能与其抑制钙离子内流有关,但此作用机制中NO和雌激素受体的作用并不显著。白藜芦醇这种抗心律失常作用对于心血管系统具有一定的保护意义。     

植物性雌激素genistein对哇巴因所致豚鼠乳头状肌迟后去极化及触发活动的效应

应用标准玻璃微电极技术,研究了植物性雌激素genistein(GST)对哇巴因所引起的豚鼠乳头状肌迟后去极化（DAD）及触发活动（TA）的效应,结果如下：（1）预先给予是GST（10,50,100umol/L)剂量依赖性地抑制哇巴因（1umol/L)所引起的鼠乳头状肌DAD及TA;（2）预先应用一氧化氮合酶抑制剂L－NAME（1mmol/L),不影响GST（50μmol/L）对DAD及TA的效应;（3）单独应用17β－雌二醇（E2,5μmol/L）或GST（10μmol/L）对DAD及TA无明显影响,而联合应用相同剂量的GST和E2则产生明显儿应,以上结果提示,GST可能通过抑制钙离子内流从而具有抗心律失常作用,这对于心血管系统的保护有一定意义。     

Fluorescence changes in human gamma-globulin induced by free-radical activity

Low-intensity ultraviolet irradiation was used to generate free-radical activity in lipid-free human gamma-globulin. The changes were monitored by fluorescence spectroscopy and gel filtration chromatography. The pattern and the effect of thiol compounds, free-radical scavengers and antioxidants point to a free-radical-mediated process. Initial energy uptake was probably in the region of aromatic amino acid residues, followed by complex intramolecular rearrangements. Irradiation led to the formation of molecular species and complexes whose fluorescence characteristics were different from those of native gamma-globulin and indistinguishable from those observed in inflammatory exudates.     

Leishmania major: species specific delayed hypersensitivity reaction induced by exogenous secreted antigen in the guinea pig

The cellular response to Leishmania major (L. major) is usually evaluated in vivo by the delayed-type-hypersensitivity (DTH) test using leishmanin. Leishmanin can give false-positive reactions in areas where there is a background of leishmaniasis. In a previous study, it was shown that a 56 kDa antigen purified from promastigote and culture supernatant of L. major induce strong DTH reactions in sensitized guinea pigs. In this study, the species-specificity of this antigen was further investigated. Three groups of guinea pigs were sensitized with L. major, L. tropica, and L. infantum and both flanks of sensitized animal were injected intradermally with purified 56 kDa antigen or soluble leishmania antigen (SLA). The extent of indurations were measured after 24, 48, and 72 h. In animals which were sensitized with three species of leishmania, only those immunized with L. major showed skin reactions to purified antigen by an increase in skin thickness. Since complex antigen mixtures such as SLA and leishmanin show cross-reactivity and can be non-specific, the result obtained here suggest that 56 kDa antigen may be a useful diagnostic tool for species specific diagnosis in field studies of leishmaniasis.     

Effect of staphylococcal toxin and antistaphylococcal gamma-globulin on the electrical and contractile activity of the guinea pig myocardium

A study was made of the action of staphylococcal toxin (ST) and its combination with antistaphylococcal gamma-globulin (ASGG) on intracellular potentials (rest potential--RP, and action potential--AP), and isometric contractions of guinea-pig auricle. ST (initial concentration 18.10(-2)Lh) diluted with normal Tyrode's solution at 1:1000, 1:100 and 1:10 (spontaneously active preparations), and Tyrode's solution with 13.5 mM KCl (evoked activity of preparations), significantly increased the duration of AP of myocardial cells. In evoked activity of preparations, RP and the amplitude of AP declined as the concentration of ST was raised. The amplitude of isometric contractions and maximal rates of their growth and fall increased under the effect of ST (1:1000) and decreased at 1:100 and 1:10. ASGG combined with ST (1:100) did not produce any protective effect on the myocardium. On the contrary, it provoked a still greater inhibition of contractility. The inhibitory action of combined ST and ASGG was seen at all ratios of ST to ASGG (use was made of ASGG shortage, equivalent amount and excess as regards ST) and reached 50% for all study characteristics of contractility. Anatoxin (inactivated toxin) combined with ASGG also produced a cardiodepressant action which was manifested in an approximately 50% decrease in the maximal rate of the growth and fall of contractions in the absence of significant changes in the contraction amplitude.     

Characterization of L-threonine deaminase activity of guinea pig liver induced by a high protein diet

In a foregoing paper, we demonstrated that under equilibrated diet conditions, guinea pig liver L-threonine deaminase activity should be allocated to two distinct enzymes: a specific L-threonine deaminase without activity toward L-serine and a L-serine deaminase having a secondary activity toward L-threonine. In the present work, we observed that a high protidic diet caused an elevation of total threonine deaminase activity. Thus purification of guinea pig liver L-threonine deaminase was attempted, using ultracentrifugation, salt precipitation, heat treatment, ion exchange chromatography on DEAE Sephacel, Sephadex G 200 molecular sieve, 2 amino-2 methyl-1 propanol linked CH 4B Sepharose chromatography. The weak variations of the ratios of specific activities respectively toward L-threonine and L-serine observed at each stage of the purification procedure indicated that both activities are very likely supported by a single enzyme preexisting in the liver of guinea pigs fed an equilibrated diet. No isoenzyme was evidenced by polyacrylamide gel electrophoresis or DEAE Sephacel chromatography. Moreover, our purification procedure demonstrated that not only inducible L-threonine deaminase guinea pig liver activity was due to L-serine deaminase, but also that an initially existing specific L-threonine deaminase activity paradoxically disappeared with a protein rich diet.     

An indomethacin-sensitive contraction induced by beta-antagonists in guinea pig airways

Beta-adrenergic receptor (beta-AR) antagonists have been associated with increased airway reactivity in asthmatics and potentiation of contractile stimuli in animal models. In the present study, using an in vitro model of tracheal preparations from guinea pigs, we show that the beta-AR antagonists propranolol and pindolol induce a smooth muscle contraction. A prerequisite for this contraction is that the airway preparations have been pre-treated with an beta-AR agonist. Our data show that the contractile effect of beta-AR antagonists is not a simple consequence of reversing the agonist-induced relaxation. Furthermore, the effect seems to be mediated through interaction with beta2-ARs since the response is stereo-selective, and the selective beta1-AR receptor antagonist atenolol did not induce any contractile response. SQ 29,546, a thromboxane A2 antagonist; MK 886, a lipoxygenase inhibitor; and indomethacin, a cyclooxygenase inhibitor significantly inhibited the contractions of the tracheal preparations induced with propranolol or pindolol. We put forward the hypothesis that the contractile effect of the beta-AR antagonist is a consequence of their inverse agonist activity, which is only evident when the receptor population have a higher basal activity. Our results indicate a novel additional explanation for the known side effect, bronchoconstriction, of beta-AR antagonist.     

Mechanisms underlying the contraction induced by bradykinin in the guinea pig epithelium-denuded trachea

This study investigates some of the mechanisms by which bradykinin (BK) triggers contraction of epithelium-denuded strips of guinea pig trachea (GPT). Cumulative or single additions of BK, T-BK, L-BK, or ML-BK in the presence of captopril (30 microM) produced graded GPT contractions with the following rank order of potency (EC50 level): T-BK (31.3 nM) > BK (40.0 nM) > L-BK (56.0 nM) > ML-BK (77.0 nM). BK-induced contraction (100 nM) in GPT was completely inhibited by either HOE 140 or NPC 17731 with mean IC50 values of 17 and 217 nM, respectively. Addition of BK (100 nM) at 30 min intervals, induced progressive tachyphylaxis, which was complete after 4 h. The tachyphylaxis induced by BK was unaffected by L-NOARG (nitric oxide synthase inhibitor, 100 microM) or valeryl salicylate (a cyclooxygenase-1 (COX-1) inhibitor, 30 microM), but was prevented by a low concentration of indomethacin, diclofenac (non-selective COX inhibitors, 3 nM each) or by NS 398 (a COX-2 inhibitor, 10 nM). Furthermore, higher concentrations of indomethacin, diclofenac, phenidone (a lypooxygenase (LOX) and COX inhibitor), or NS 398, caused graded inhibition of BK-induced contraction, with mean IC50 values of 0.28, 0.08, 46.37, and 0.15 microM, respectively. Together, these results suggest that BK-induced contraction in GPT involves activation of B2 receptors and release of prostanoids from COX-2 pathway. Furthermore, the tachyphylaxis induced by BK was insensitive to the nitric oxide and COX-1 inhibitors, but was prevented by non-selective and selective COX-2 inhibitors, indicating a mediation via COX-2-derived arachidonic acid metabolites.