美哌隆对麻醉的正常血压大鼠的降压作用

我们用麻醉的正常血压大鼠,大鼠的自体灌液后肢分别研究了美哌隆的降压作用强度、部位、维持时间和对心率的影响。实验结果提示:美哌隆降低动脉血压的作用除依赖于它对外周α_1受体的选择性阻滞外,还依赖于它对外周阻力血管的直接扩张作用。美哌隆在降压的同时也减慢心率,其降压作用和负性频率作用与剂量有关。     

Matrix Metalloproteinase-2 and Tissue Inhibitor of Metalloproteinase-1 in the Retinal Pigment Epithelium and Interphotoreceptor Matrix: Vectorial Secretion and Regulation

Matrix metalloproteinases (MMPs) and the tissue inhibitors of metalloproteinases (TIMPs) play an essential role in both normal and pathological extracellular matrix degradation, and a TIMP has been associated with at least one type of retinal degeneration. We have studied expression of MMP-2 and TIMP-1 by zymography, immunocytochemistry, and immunoblotting in the retinal pigment epithelium (RPE) from normal, aged and diseased retinas. MMPs and TIMPs were found in the rat RPE, interphotoreceptor matrix (IPM), and in media conditioned by human and rat RPE in culture. In other polarized cells, MMPs and TIMP-2 are secreted vectorially towards the basal lamina. In the RPE, however, MMP-2 and TIMP-1 were secreted preferentially from the apical surface, the surface bordering the IPM. These findings provide new evidence that MMPs and TIMPs could play a role in the turnover of IPM components.Cell homogenates and conditioned media from RPE isolated from mutant Royal College of Surgeons (RCS) rats with inherited retinal dystrophy had similar amounts of MMP-2 and TIMP-1 as those from congenic control rats. The secretion of MMP-2 and TIMP-1 from RPE cell cultures isolated from young and aged human donors varied widely. However, with increasing cell passage number, secretion of MMPs and TIMPs from human RPE increased dramatically. Also, growing human RPE on bovine corneal endothelial cell-generated extracellular matrix instead of plastic reduced the secretion of both MMPs and TIMPs. These data suggest that the integrity of Bruch's membrane may serve to regulate RPE functions in MMP and TIMP secretion and that extracellular matrices contain signals that regulate MMP and TIMP synthesis and/or secretion by the RPE.     

Effects of recombinant humanen dothelial-derived interleukin-8 on hemorhagic shock in rats

目的：研究重组人内皮细胞衍生的白细胞介素－８（ＩＬ８）对失血性休克的作用．方法：大鼠股动脉放血至ＭＡＢＰ５３２ｋＰａ，维持９０ｍｉｎ，复制晚期失血性休克模型．输血后，静脉注射ＩＬ８２５０μｇ·ｋｇ－１．放免法测定血浆ＥＴ１和６ＫＰＧＦ１α含量．结果：给予ＩＬ８后，ＭＡＢＰ显著提高，休克状态改善，２ｈ存活率相应提高；休克晚期血浆ＥＴ１水平比正常明显升高（２１±４ｖｓ８２±１８ｎｇ·Ｌ－１，Ｐ＜００１），血浆６ＫＰＧＦ１α含量明显降低（１０７±１２ｖｓ１５７±１１ｎｇ·Ｌ－１，Ｐ＜００１）．ＩＬ８显著降低血浆ＥＴ１水平（１０±４ｎｇ·Ｌ－１，Ｐ＜００１），提高血浆６ＫＰＧＦ１α含量（３６８±１６ｎｇ·Ｌ－１，Ｐ＜００１）．结论：ＩＬ８具有较好的抗休克作用．     

Polysialylated Neural Cell Adhesion is Involved in Target-induced Morphological Differentiation of Arcuate Dopaminergic Neurons

We have previously shown that the morphological and biochemical maturation of developing rat hypothalamic dopaminergic neurons is accelerated when they are cocultivated with pituitary intermediate lobe cells, one of their targets. Only two subsets of hypothalamic dopaminergic neurons (arcuate, A12, and periventricular, A14, nuclei) may project to the pars intermedia. In order to determine whether the two populations are equally responsive to coculture conditions, we microdissected the hypothalamus of 17-day-old rat fetuses in two fragments containing cell bodies from the A12 and from the A14 regions, prepared neuronal cultures from both portions and incubated them separately with intermediate lobe cells. The presence of intermediate lobe cells increased tyrosine hydroxylase levels in both dopaminergic neuron subsets, but morphological differentiation was accelerated in dopaminergic neurons originating in the arcuate nucleus only. We then investigated whether physical contact between developing arcuate neurons and their target cells was a prerequisite of the morphological effect by interposing a semipermeable membrane between cultivated neurons and intermediate lobe cells in transwell culture dishes. The morphological effect was no longer observed under transwell coculture conditions, pointing to the involvement of membrane-bound molecules. Accordingly, the stimulating effect of coculture on arcuate dopaminergic neurons was completely abolished by the removal of polysialic acid on neural cell adhesion molecules by endoneuraminidase N treatment. Thus, maturation of A12 and A14 dopaminergic neurons exhibits differential susceptibility to intermediate lobe target cells, and polysialylated-NCAM is required for the contact-dependent effect.     

Glucuronidation of Entacapone, Nitecapone, Tolcapone, and Some Other Nitrocatechols by Rat Liver Microsomes

Purpose. Nitrocatechol COMT inhibitors are a new class of bioactive compounds, for which glucuronidation is the most important metabolic pathway. The objective was to characterize the enzyme kinetics of nitrocatechol glucuronidation to improve the understanding and predicting of the pharmacokinetic behavior of this class of compounds. Methods. The glucuronidation kinetics of seven nitrocatechols and 4-nitrophenol, the reference substrate for phenol UDP-glucuronosyltrans-ferase activity, was measured in liver microsomes from creosote-treated rats and determined by non-linear fitting of the experimental data to the Michaelis-Menten equation. A new method that combined densitometric and radioactivity measurement of the glucuronides separated by HPTLC was developed for the quantification. Results. Apparent K_m values for the nitrocatechols varied greatly depending on substitution pattern being comparable with 4-nitrophenol (0.11 mM) only in the case of 4-nitrocatechol (0.19 mM). Simple nitrocatechols showed two-fold V_max values compared with 4-nitrophenol (68.6 nmol min^–1 mg^–1), while all disubstituted catechols exhibited much lower glucuronidation rate. V_max/K_m values were about 10 times higher for monosubstituted catechols compared to disubstituted ones. The kinetic parameters for COMT inhibitors were in the following order: K_m nitecapone >> entacapone > tolcapone; V_max nitecapone > entacapone > tolcapone; V_max/K_m tolcapone > nitecapone > entacapone. Conclusions. Nitrocatechols can in principle be good substrates of UGTs. However, substituents may have a remarkable effect on the enzyme kinetic parameters. The different behaviour of nitecapone compared to the other COMT inhibitors may be due to its hydrophilic 5-substituent. The longer elimination half-life of tolcapone in vivo compared to entacapone could not be explained by glucuronidation kinetics in vitro.     

N-ω-Carbethoxypentyl-4-quinolones: A New Class of Leukotriene Biosynthesis Inhibitors

6-[(4-Quinolinyl)oxy]hexanoic acids and the corresponding esters were designed and synthesized as inhibitors of the production of arachidonic acid metabolites. The inhibitory activities were assayed in vitro by evaluation of serum leukotriene B₄ and thromboxane B₂ production. While all 6-[(4-quinolinyl)oxy]hexanoic acids and their esters proved to be inactive, the N-alkyl-4-quinolones, obtained as by-products in their synthesis, were found to be a new class of leukotriene biosynthesis inhibitors.     

Characterization of the human cytochrome P450 enzymes involved in the metabolism of dihydrocodeine

Aims Using human liver microsomes from donors of the CYP2D6 poor and extensive metabolizer genotypes, the role of individual cytochromes P-450 in the oxidative metabolism of dihydrocodeine was investigated.
Methods The kinetics of formation of N- and O -demethylated metabolites, nordihydrocodeine and dihydromorphine, were determined using microsomes from six extensive and one poor metabolizer and the effects of chemical inhibitors selective for individual P-450 enzymes of the 1A, 2A, 2C, 2D, 2E and 3A families and of LKM1 (anti-CYP2D6) antibodies were studied.
Results Nordihydrocodeine was the major metabolite in both poor and extensive metabolizers. Kinetic constants for N -demethylation derived from the single enzyme Michaelis-Menten model did not differ between the two groups. Troleandomycin and erythromycin selectively inhibited N -demethylation in both extensive and poor metabolizers. The CYP3A inducer, α-naphthoflavone, increased N -demethylation rates. The kinetics of formation of dihydromorphine in both groups were best described by a single enzyme Michaelis-Menten model although inhibition studies in extensive metabolizers suggested involvement of two enzymes with similar K _m values. The kinetic constants for O -demethylation were significantly different in extensive and poor metabolizers. The extensive metabolizers had a mean intrinsic clearance to dihydromorphine more than ten times greater than the poor metabolizer. The CYP2D6 chemical inhibitors, quinidine and quinine, and LKM1 antibodies inhibited O -demethylation in extensive metabolizers; no effect was observed in microsomes from a poor metabolizer.
Conclusions CYP2D6 is the major enzyme mediating O -demethylation of dihydrocodeine to dihydromorphine. In contrast, nordihydrocodeine formation is predominantly catalysed by CYP3A.     

Inadequate Erythropoietin Response to Anaemia in HIV Patients: Relationship to Serum Levels of Tumour Necrosis Factor-Alpha, Interleukin-6 and Their Soluble receptors

Severe anaemia is a frequent complication in advanced HIV infection. In our study we investigated the interaction between cytokine network, HIV infection and erythropoietin (Epo) response with increasing anaemia levels. No correlations could be established between circulating tumour necrosis factor (TNF)-alpha and any of the examined parameters. However, a negative correlation was found between haemoglobin values and soluble TNF receptor levels (sTNF-R-I: r  = −0.54; P  < 0.001; sTNF-R II: r  = −0.47; P  < 0.001) as well as interleukin-6 levels ( r  = −0.29; P  < 0.001). In contrast, no significant increase in log[Epo], counterbalancing haemoglobin decline and paralleling the rise in sTNF receptors, was found. In patients classified as stage III, according to the Centers for Disease Control (CDC) classification, the erythropoietin response was significantly more impaired than in patients from CDC groups I and II ( P  < 0.001). The results of this study suggest that similar to its action in vitro , activation of the TNF/TNF-R system may impair erythropoietin production in HIV-associated anaemia. Due to the brief half-life of TNF-α, this activation is particularly reflected by elevations of soluble TNF receptor levels.     

Spatially and Temporally Regulated Modification of the Receptor-like Protein Tvrosine Phosphatase ζ/β isoforms with Keratan Sulphate in the Developing Chick Brain

Protein tyrosine phosphatase ζ (PTPζRPTPβ) is a proteoglycan-type receptor-like protein tyrosine phosphatase specifically expressed in the brain. In addition to the transmembrane form (PTPζ-A), the extracellular splice variant (PTPζ-S) occurs as a major soluble chondroitin sulphate proteoglycan in the brain. We prepared antibodies which specifically recognize PTPζ-A and -S, and analysed the carbohydrate structures on the two PTPζ isoforms in the developing chick brain. lmmunoprecipitation experiments using these antibodies revealed that almost all of the keratan sulphate recognized by a monoclonal antibody (5D4) was exclusively bound to PTPζ-A and PTPζ-S. Addition of keratan sulphate to these proteoglycans markedly increased from embryonic day (E) 11, in contrast to the addition of Le^X and HNK-1 carbohydrates, which gradually increased during development in accordance with expression of the core proteins, suggesting that keratan sulphate modification plays some specific roles. Moreover, at the early embryonic stage keratan sulphate was observed only in several restricted regions, especially at boundary regions such as the roof plate of the tectum, the zona limitans intrathalamica in the diencephalon, and the mesencephalon-metencephalon boundary. At the mesencephalon-metencephalon boundary, keratan sulphate modification of PTPζ isoforms was specifically observed from E3 to E6 on a ring of cells encircling the neural tube and their radially oriented processes, which were identified as radial glial fibres. This expression pattern of keratan sulphate spatiotemporally corresponded well to the formation of the fovea isthmi, a groove separating the mesencephalon from the metencephalon. These results suggest that carbohydrates including keratan sulphate on PTPζ isoforms play important roles in brain development by modulating the cell-cell and/or cell-substrate interactions mediated by these molecules.     

Chronic vitamin E treatment prevents defective endothelium-dependent relaxation in diabetic rat aorta

Summary We examined the effect in rats of 2 months of streptozotocin-induced diabetes mellitus on relaxation and contraction of aortas in vitro. A further diabetic group was treated from time of diabetes induction with a 1% dietary supplement of vitamin E. Diabetes caused a 26.5% deficit (p<0.001) in maximum endothelium-dependent relaxation to acetylcholine in phenylephrine-precontracted aortas. This was 64.3% attenuated (p<0.01) by vitamin E treatment; maximum relaxation was not significantly altered compared to non-diabetic rats. Vitamin E treatment of non-diabetic rats did not significantly affect acetylcholine-induced relaxation. Diabetes or treatment did not significantly alter acetylcholine sensitivity. Endothelium-independent relaxation response to glyceryl trinitrate was not affected by diabetes or vitamin E treatment, indicating that vascular smooth muscle responses to nitric oxide remained unaltered. There was a 35.4% reduction in the maximum contractile response to phenylephrine with diabetes (p<0.05) which was unaffected by vitamin E treatment. The data suggest that the chronic deficit in nitric oxide-mediated endothelium-dependent relaxation in diabetes depends largely upon excess activity of reactive oxygen species. Treatment with vitamin E to increase free radical scavenging specifically protected vascular endothelium although it had no effect on deficits in vascular smooth muscle contractile responses.Abbreviations NO Nitric oxide - ARI aldose reductase inhibitor - ACH acetylcholine - GTN glyceryl trinitrate - GSH reduced form of glutathione - EC₅₀ effective concentration for 50% of the maximal response