大鼠急性氧中毒后全脑细胞能量代谢的活体^31P磁共振谱 …

目的：探讨大鼠急性氧中毒后脑的能量代谢产物与脑细胞内ＰＨ变化的规律。方法：采用磁共振方法,用４．７Ｔ动物磁共振谱仪,检测氧中毒后不同时程各种磷酸化合物与无机磷酸根（Ｐｉ）、磷酸肌酸（ＰＣｒ）与γ－ＡＴＰ以及β－ＡＴＰ与Ｐｉ之间的比值,并根据Ｐｉ的化学位移推算脑细胞内ＰＨ值。结果：氧中毒组物舱１和３小时后ＰＣｒ／Ｐｉ,ＰＣｒ／γ－ＡＴＰ以及β－ＡＴＰ／Ｐｉ值均显著降低;５ｈ后恢复正常;２４和４８小时     

2型糖尿病与钙,磷代谢及相关激素的关系

目的 观察２型糖尿病患者钙、磷代谢及相关激素的变化及对骨代谢的影响。方法 测定２０例健康对照者和６０例２型糖尿病患者血甲状旁腺素（ＰＴＨ）、降钙素（ＣＴ）、２５羟维生素Ｄ３「「２５（ＯＨ）Ｄ３」」、环磷酸腺苷（ｃＡＭＰ）和血、尿钙（Ｃａ）、磷（Ｐ）、镁（Ｍｇ）,糖基化血红蛋白（ＨｂＡｌｃ）、２４ｈ尿和２４ｈ尿白蛋白定量等指标。结果 ２型糖尿病患者血ＰＴＨ水平显著高于对照组（Ｐ〈０．０１）,ＣＴ水平     

Involvement of cyclic nucleotide-dependent protein kinases in cyclic AMP-mediated vasorelaxation

1. The involvement of cyclic AMP-dependent protein kinase (PKA) and cyclic GMP-dependent protein kinase (PKG) in the effects of cyclic AMP-elevating agents on vascular smooth muscle relaxation, cyclic nucleotide dependent-protein kinase activities and ATP-induced calcium signalling ([Ca²⁺]_i) was studied in rat aorta. Cyclic AMP-elevating agents used were a β-adrenoceptor agonist (isoprenaline), a phosphodiesterase 3 (PDE3) inhibitor (SK&F 94120) and a PDE4 inhibitor (rolipram).
2. In rat intact aorta, the relaxant effect induced by isoprenaline (0.01–0.3 μM) was decreased by a specific inhibitor of PKA, H-89, whereas a specific inhibitor of PKG, Rp-8-Br-cyclic GMPS, was without effect. No significant difference in PKA and PKG activity ratios was detected in aortic rings when isoprenaline 10 μM was used. At the same concentration, isoprenaline did not modify ATP-induced changes in [Ca²⁺]_i in smooth muscle cells. Neither H-89 nor Rp-8-Br-cyclic GMPS modified this response. These findings suggest that PKA is only involved in the relaxant effect induced by low concentrations of isoprenaline (0.01–0.3 μM), whereas for higher concentrations, other mechanisms independent of PKA and PKG are involved.
3. The relaxant effects induced by SK&F 94120 and rolipram were inhibited by Rp-8-Br-cyclic GMPS with no significant effect of H-89. Neither SK&F 94120, nor rolipram at 30 μM significantly modified the activity ratios of PKA and PKG. Rolipram inhibited the ATP-induced transient increase in [Ca²⁺]_i. This decrease was abolished by Rp-8-Br-cyclic GMPS whereas H-89 had no significant effect. These results suggest that PKG is involved in the vascular effects induced by the inhibitors of PDE3 and PDE4. Moreover, since it was previously shown that PDE3 and PDE4 inhibitors only increased cyclic AMP levels with no change in cyclic GMP level, these data also suggest a cross-activation of PKG by cyclic AMP in rat aorta.
4. The combination of 5 μM SK&F 94120 with rolipram markedly potentiated the relaxant effect of rolipram. This relaxation was decreased by H-89 and not significantly modified by Rp-8-Br-cyclic GMPS. Moreover, the association of the two PDE inhibitors significantly increased the activity ratio of PKA without changing the PKG ratio. The present findings show that PKA rather than PKG is involved in this type of vasorelaxation. The differences in the participation of PKA vs PKG observed when inhibitors of PDE3 and PDE4 were used alone or together could be due to differences in the degree of accumulation of cyclic AMP, resulting in the activation of PKA or PKG which are differently localized in the cell.
5. These findings support a role for both PKA and PKG in cyclic AMP-mediated relaxation in rat aorta. Their involvement depends on the cellular pathway used to increase the cyclic AMP level.

     

Negative chronotropic actions of endothelin-1 on rabbit sinoatrial node pacemaker cells

1. The effects of endothelin-1 (ET-1) on sinoatrial (SA) node preparations of the rabbit heart were studied by means of whole-cell clamp techniques.
2. ET-1 at 1 nM slowed the spontaneous beating activity and rendered half of the cells quiescent. At a higher concentration of 10 nM, the slowing and cessation of spontaneous activity were accompanied by hyperpolarization.
3. In voltage-clamp experiments, ET-1 decreased the basal L-type Ca²⁺ current (I_Ca(L)) dose-dependently with a half-maximal inhibitory concentration (EC₅₀) of 0.42 nM and maximal inhibitory response (E_max) of 49.5%. The delayed rectifying K⁺ current (I_K) was also reduced by 33.2±11.1% at 1 nM. In addition, an inwardly rectifying K⁺ current was activated by ET-1 at higher concentrations (EC₅₀=4.8 nM). These ET-1-induced changes in membrane currents were abolished by BQ485 (0.3 μM), a highly selective ET_A receptor antagonist.
4. When I_Ca(L) was inhibited by ET-1 (1 nM), subsequent application of 10 μM ACh showed no additional decrease in I_Ca(L), suggesting the involvement of cyclic AMP in the effects of ET-1 on I_Ca(L). In contrast, 1 nM ET-1 further decreased I_Ca(L) in the presence of 10 μM ACh, suggesting that ET-1 activates some additional mechanism(s) which inhibit I_Ca(L). The ET-1-induced I_Ca(L) inhibition was abolished by protein kinase A inhibitory peptide (PKI, 20 μM) or H-89 (5 μM). However, the I_Ca(L) inhibition was not affected by methylene blue (10 μM), suggesting a minor role for cyclic GMP in the effect of ET-1 under basal conditions.
5. ET-1 failed to inhibit I_Ca(L) when the pipette contained GDPβS (200 μM). However, incubation of the cells with pertussis toxin (PTX, 5 μg ml⁻¹, >6 h) only reduced the ET-1-induced inhibition to 21.5±9.5%, whereas it abolished the inhibitory effect of ACh on I_Ca(L).
6. Intracellular perfusion of 8-bromo cyclicAMP (8-Br cyclicAMP, 500 μM) attenuated, but did not abolish the inhibitory effect of ET-1 on I_Ca(L). This 8-Br cyclicAMP-resistant component (17.5±14.4%, n=20) was not affected by combined application of 8-Br cyclicAMP with 8-bromo cyclicGMP (500 μM), ryanodine (1 μM) or phorbol-12-myristate-13-acetate (TPA; 50 nM).
7. In summary, ET-1 exerts negative chronotropic effects on the SA node via ET_A-receptors. ET-1 inhibits both I_Ca(L) and I_K, and increases background K⁺ current. The inhibition of I_Ca(L) by ET-1 is mainly due to reduction of the cyclicAMP levels via PTX-sensitive G protein, but some other mechanism(s) also seems to be operative.

     

Interleukin-1β-induced, nitric oxide-dependent and -independent inhibition of vascular smooth muscle contraction

Stimulation of vascular smooth muscle by bacterial lipopolysaccharide has been shown to produce interleukin-1β and to induce vasodilation in septic shock. To understand the mechanisms of interleukin-1β-induced relaxation, we examined the effects of interleukin-1β on contractility and cyclic GMP contents of vascular smooth muscle. After treatment of the rat aorta with interleukin-1β (20 ng/ml) for 6 h, the cyclic GMP content increased and the contraction induced by phenylephrine (1 μM) was partially inhibited. An inhibitor of nitric oxide (NO) synthase, N^G-monomethyl-

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-arginine (

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-NMMA, 100 μM), prevented the inhibitory effect of interleukin-1β. After treatment with interleukin-1β for 24 h, the phenylephrine-induced contraction was inhibited more strongly. Neither

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-NMMA (100 μM) nor aminoguanidine (100 μM) reversed the inhibition, whereas methylene blue (10 μM) partially reversed the inhibition. After treatment with interleukin-1β for 12 or 24 h, the cyclic GMP content increased but to a level lower than that obtained with a 6-h treatment. The effects of sodium nitroprusside (1 μM) to inhibit the phenylephrine-induced contraction and to increase the cyclic GMP content were markedly suppressed by the 24-h interleukin-1β treatment. In contrast, the 24-h interleukin-1β treatment did not change the ability of 8-bromo-cGMP to relax the phenylephrine-stimulated aorta. Addition of

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-NMMA (1 mM) during the 24 h treatment prevented NO production and preserved the sodium nitroprusside-induced cGMP generation by interleukin-1β. The 24 h interleukin-1β treatment increased the threshold concentration of KCl needed to induce contraction without changing the maximum contraction. In the presence of 25.4 mM KCl or the non-selective K⁺ channel inhibitor, tetraethylammonium, the inhibitory effect of the 24-h interleukin-1β treatment on phenylephrine-induced contraction was restored. These results suggest that interleukin-1β inhibits vascular smooth muscle contraction by a time-dependent, dual mechanism. After a 6-h treatment with interleukin-1β, the NO/cyclic GMP system is activated. After a 24-h interleukin-1β treatment, in contrast, the NO/cyclic GMP system may be desensitized and the contraction of vascular smooth muscle is inhibited by another mechanism, possibly membrane hyperpolarization.     

An endogenous A2B adenosine receptor coupled to cyclic AMP generation in human embryonic kidney (HEK 293) cells

1. Cyclic AMP generation by adenosine analogues was examined in human embryonic kidney (HEK 293) cells by use of a [³H]-adenine pre-labelling methodology.
2. Adenosine analogues showed the following rank order of potency (pD₂ value): 5′-N-ethylcarboxamidoadenosine (NECA, 5.24)>2-chloroadenosine (4.41) ⩾ adenosine (4.19)=N⁶-(2-(4-aminophenyl)-ethylamino)adenosine (APNEA, 4.11). The A_2A-selective agonist {"type":"entrez-protein","attrs":{"text":"CGS21680","term_id":"878113053","term_text":"CGS21680"}}CGS21680 failed to elicit a significant stimulation of cyclic AMP generation at concentrations below 30 μM.
3. Of these agents, NECA was observed to exhibit the greatest intrinsic activity, while in comparison maximal responses to adenosine (76±8% NECA response), 2-chloroadenosine (70±6%) and APNEA (40±3%) were significantly reduced.
4. Antagonists of the NECA-evoked cyclic AMP generation showed the rank order of apparent affinity (apparent pA₂ value): CGS 15943 (7.79)=XAC (7.74)>DPCPX (7.01)=PD115199 (6.93)=8FB-PTP (6.80)>KF 17837 (5.98)>3-propylxanthine (5.13).
5. Agarose gel electrophoresis of the products of the polymerase chain reaction, with cDNA generated from HEK 293 cell total RNA showed virtually identical patterns and nucleotide sizes in comparison with the vector for the full length human brain A_2B adenosine receptor.
6. We concluded that HEK 293 cells express an endogenous adenosine receptor coupled to cyclic AMP generation which is of the A_2B subtype.

     

Fertilization and early embryology: Autocrine/paracrine function of transforming growth factor-{beta}1 in porcine granulosa cells

The present study was undertaken to investigate the effectsof transforming growth factor (TGF)-1 on ovarian steroidogenesisin immature or moderately mature porcine granulosa cells invitro. TGF-1 (0.01–10 ng/ml) significantly attenuatedprogesterone release from the basal and follicle stimulatinghormone-stimulated porcine granulosa cells, and significantlyincreased DNA synthesis. TGF-1 also significantly increasedthe extracellular accumulation of cyclic AMP, but did not changethe production of inositol phosphate or the intracellular calciumconcentration in these cells. Thus, TGF-1 appears to have adirect effect on porcine granulosa cell function, regulatingthe differential synthesis of progesterone mainly via the intracellularsignal transduction of the cyclic AMP—protein kinase Apathway. This growth factor may play a physiologically significantrole in controlling differentiation of immature and moderatelymature porcine granulosa cells via an autocrine/paracrine mechanism.     

Presynaptic α2A-adrenoceptors inhibit the release of endogenous dopamine in rabbit caudate nucleus slices

₂-Adrenoceptors modulating the release of dopamine were identified and characterized in slices of the head of the rabbit caudate nucleus. Release of endogenous dopamine was measured by fast cyclic voltammetry as the increase in the extracellular concentration of dopamine elicited by electrical stimulation. The electrochemical signal was identified as dopamine by means of the oxidation potential, the voltammogram and the fact that the signal was not changed by desipramine, which inhibits the high affinity uptake of noradrenaline, but was greatly increased by nomifensine, which in addition inhibits the high affinity uptake of dopamine.Stimulation by 6 pulses/100 Hz increased the extracellular concentration of dopamine by about 85 nM. The selective ₂-adrenoceptor agonist 5-bromo-6-(2-imidazolin-2-ylamino)-quinoxaline (UK 14,304) reduced this release with an EC₅₀ of 173 nM and by maximally 75%. The ₂-adrenoceptor agonists clonidine and oxymetazoline only tended to cause a decrease. Six drugs, including oxymetazoline, were tested as antagonists against UK 14,304. Their order of antagonist potency (pK_D values in brackets) was rauwolscine (8.0) > oxymetazoline (7.5) > 2-(2,6-dimethoxyphenoxyethyl)aminomethyl-1,4-benzodioxane (WB 4101; 7.3) > phentolamine (7.1) > corynanthine (5.1) prazosin (< 6). Given alone, the antagonists did not change the release of dopamine elicited by 6 pulses/100 Hz, and the same was true for the dopamine receptor antagonist sulpiride. When caudate slices were stimulated by 10 pulses/1 Hz, sulpiride increased the release of dopamine. Desipramine and rauwolscine, in contrast, again caused no change.It is concluded that dopaminergic axons in the rabbit caudate nucleus possess release-inhibiting ₂-adrenoceptors. The antagonist affinities indicate that they belong to the _2A subtype. In this, they agree with all presynaptic ₂-autoreceptors studied so far in rabbits as well as with the ₂-heteroreceptors modulating the release of serotonin in rabbit brain cortex, suggesting that at least the majority of presynaptic ₂-adrenoceptors in the rabbit are _2A. The agonist sensitivity of the caudate presynaptic ₂-adrenoceptors is low in comparison with cerebrocortical presynaptic ₂-autoreceptors, possibly due to absence of a receptor reserve. Correspondence to: N. Limberger at the above address     

Thiopentone inhibits beta-adrenergic responses in myocardial tissue

The purpose of this study was to determine the importance of inhibition of beta-adrenergic function in thiopentone-induced myocardial depression. Using an isolated, electrically stimulated rat left atria model, contractile dose-response curves to thiopentone (200 μM, 400 μM, 600 μM, 800 μM) were shifted to the right in preparations treated with 10^{− 3} M dibutyryl cyclic adenosine monophosphate (cAMP) compared with atria stimulated with 10^{− 6} M isoprenaline, demonstrating that inhibition of beta-adrenergic mechanisms by thiopentone is physiologically important. Depression by thiopentone was similar in atria treated with 10^{− 5} M forskolin compared with preparations stimulated with 10^{− 6} M isoprenaline, indicating that thiopentone does not block beta-adrenergic receptors. It is concluded that thiopentone depresses myocardial function by several mechanisms, one of which involves inhibition of the adenyl cyclase cascade. The adenyl cyclase enzyme is a likely site where thiopentone inhibits the system; however, other components of the cascade may also be involved. L’objectif de cette étude consiste à déterminer l’influence de l’inhibition de l’activité β-adrenergique sur la dépression myocardique induite par le thiopentone. A l’aide d’un modèle constitué d’une oreillette gauche de rat stimulée électriquement, la relation dose-effet du thiopentone sur la contractilité (200 μM, 400 μM, 600 μM, 800 μM) se déplace vers la droite dans des préparations traitées avec de l’adénosine monophosphorique cyclique (cAMP) 10^{− 3} M comparativement à des oreillettes stimulées avec de l’isoprénaline 10^{− 6} M, ce qui démontre que l’inhibition β-adrénergique provoquée par le thiopentone est physiologiquement importante. La dépression de l’oreillette provoquée par le thiopentone est identique à celle que produit la forskoline 10^{− 5} M comparativement à celle de l’isoprénaline 10^{− 6} M, ce qui indique que le thiopentone n’inhibe pas les récepteurs β-adrénergiques. Les auteurs concluent que le thiopentone déprime la fonction myocardique par plusieurs mécanismes qui impliquent l’inhibition de la cascade de l’adényl cyclase. L’inhibition du système se produit vraisemblablement au niveau de l’enzyme adényl cyclase; cependant, il est possible que d’autres éléments de la cascade de l’adényl cyclase soient impliqués.     

磷改性层柱交联累托石催化剂的积炭性能

采用有机磷化合物对层柱交联累托石催化剂进行了改性研究。考察了有机磷化合物的加入对催化剂轻瓦斯油裂化活性和积炭性能的影响。结果表明：含有适量磷化合物的层柱交联累托催化剂,焦炭产率可降低３０％,轻瓦斯油在层柱交联累托石催化剂上的裂化反应和积炭反应是并行的,而裂化活性仍保持不变。磷化合物的加入使层柱交联累托石催化剂的Ｂ酸强度增加,但积炭反应主要不是由Ｂ酸强度决定,而是与强弱Ｂ酸中心数目的比例以及Ｂ酸和Ｌ