In vitro properties of a newly established medulloblastoma cell line, MCD-1

Medulloblastomas are poorly differentiated brain tumors believed to arise from primitive pleuripotential stem cells, and tend to express mixed neuronal and glial properties. In the present study, we examined immunohistochemical and neurotransmitter phenotypic properties in a newly established medulloblastoma cell line, MCD-1. MCD-1 cells were immortal, not contact-inhibited, but did not grow in soft agar. Immunohistochemical studies showed positive staining for neurofilament protein (NF), neuron-specific enolase (NSE), synaptophysin, MAP 2, τ, NCAM 180, vimentin, and S-100 protein. The cells expressed specific uptake of glutamate, serotonin, and choline, but not GABA or dopamine. A significant increase in process extension was seen in response to agents that enhance intracellular cyclic AMP, especially 3-isobutyl-1-methylxanthine (IBMX). Process formation induced by IBMX was associated with a decrease in cell proliferation as evidenced by a reduction in numbers of cells incorporating 5-bromo-2-deoxyuridine (BrdU). No increase in process extension was observed following exposure to NGF or retinoic acid. MCD-1 cells were shown to produce transforming growth factor beta (TGFβ), and were immunopositive for mutant p53. Transfection assays with the PG13-Luc reporter plasmid, which contains a p53-responsive enhancer element and a luciferase reporter gene, suggested MCD-1 cells are deficient in wild-type p53 and do not activate p53 on treatment with the anticancer agent adriamycin. The MCD-1 cell line is suggested to represent an abnormally differentiated cell type, which has some properties consistent with a multipotent neuronal phenotype while retaining some properties of immature cells of a glial lineage. The MCD-1 cell line can be used to provide a model of a medulloblastoma cell line that is resistant to growth-controlling and anticancer agents.     

Conformation of a cyclic decapeptide analog of a repeat pentapeptide sequence of elastin: cyclo-bis(valyl-prolyl-alanyl-valyl-glycyl)

The conformation of a cyclic decapeptide analog of a repeat sequence of elastin has been determined in the crystalline state using X-ray crystallographic techniques. Tetragonal crystals were grown from a solution of the decapeptide in water; space group P4₂2₁2, a = 19.439(2) & c = 13.602(1) Å, with four formula units (C₄₀H₆₆N₁₀O₁₀·4H₂O) per unit cell. The cyclic decapeptide in the crystal exhibits exact twofold symmetry. The asymmetric unit contains one pentapeptide and two water molecules for a total of 32 nonhydrogen atoms. The structure has been determined by the application of direct methods and refined by full-matrix least squares to an R index of 0.053 for 2272 reflections with intensities greater than 2σ(I). The backbone conformation of the asymmetric pentapeptide can be described as consisting of a double β bend of Type III-I. The Type III turn has Pro (ρ= -59.3°, Ψ= -26.8°) and Ala (ρ= -65.9°, Ψ= -23.1°) at the corners while Type I turn has Ala (ρ= -65.9°, Ψ= -23.1°) and Val (ρ= -98.9°, Ψ= 8.3°) as the corner residues. The cyclic decapeptide has two such double bends linked together by Gly-Val bridges.     

单组分妥布霉素产生菌的选育

目的 提高妥布霉素产生菌的发酵单位。方法 以黑暗链霉菌UVS－51为出发菌株，采用UV和NTG为诱变剂，结合耐受妥布霉素，运用固体循环诱变筛选高产菌株。结果 获得两株高产稳定变株NS－81和NT－26，这两株菌的授瓶发酵效价分别比出发菌株提高53％和77％。经薄层层析检验，该两变株的产物仍为单一的氨甲酰妥布霉素。结论 出发菌株经UV和NTG诱变处理后结合耐自身代谢物的驯育，正变率显著提高。通过引入循环诱变筛选的思路，大大缩短的实验周期有交待 提高了诱变育种的工作效率，能在较短时间内选育到理想变株，因此，循环诱变筛选法是一种较好的选育方法。     

Pituitary adenylate cyclase-activating polypeptide (PACAP) increases prolactin release and tuberoinfundibular dopaminergic neuronal activity

Pituitary adenylate cyclase activating polypeptide (PACAP) is a hypothalamic peptide that affects anterior pituitary cell function. This study examined the effects of PACAP on prolactin (PRL) release in vivo and on tyrosine hydroxylase (TH) activity in tuberoinfundibular dopaminergic neurons in vivo and in vitro. In ovariectomized rats, intravenous injection of PACAP increased circulating PRL levels 3-fold and TH activity in the stalk-median eminence (SME) by 30%. Incubation of the SME with 1 μM PACAP in vitro increased TH activity 2-fold. Intravenous infusion of ovine PRL (oPRL) by an osmotic mini-pump for 2 days in ovariectomized rats increased TH activity in the SME 1.7-fold and reduced circulating concentrations of endogenous rat PRL to 20% of control levels. PACAP induced a 4-fold rise in endogenous rat PRL levels in oPRL-treated rats and a 30% increase in TH activity that was additive to the elevation caused by hyperprolactinemia. In suckled lactating rats, PACAP did not alter circulating PRL levels or TH activity in the SME. When pups were removed from the dams for 4–5 h, systemic injection of PACAP stimulated PRL release without altering TH activity. However, PACAP, when administered in vitro, stimulated TH activity in the SME of lactating rats separated from their pups. These data indicate that PACAP may play a role in augmenting PRL release in female rats. The PACAP-induced rise in PRL release is modest and not due to a decrease in tuberoinfundibular dopaminergic neuronal activity. PACAP increases TH activity in the tuberoinfundibular dopaminergic neurons, possibly by a direct action on nerve terminals within the median eminence.     

Synthesis and conformational analysis of cyclic pentapeptide endothelin antagonists

Two endothelin antagonists cyclo(d -Leu-d -Val-Pro-d -Asp-Trp) (IPI-147), and cyclo(d -Trp-d -Asp-Ac₃c-d -Val-Leu) (IPI-725) have been synthesized. Their solution conformations have been studied in aqueous solution by NMR spectroscopy and dynamics simulation. Activity studies show that IPI-725 is a strong ET_A antagonist, while IPI-147 is a weak ET_A antagonist. Comparison of the solution conformations of these two ET_A antagonists suggests that the difference in their activities results from their structural differences. IPI-147 contains a type II β-turn with a hydrogen bond between NH of d -Val and the C = O of d -Asp. IPI-725, on the other hand, contains two turns, a type II β-turn with a hydrogen bond between NH of d -Asp and C=O of d -Val, as well as a γ-turn with a hydrogen bond formed between d -Val NH and d -Asp carbonyl group. Therefore IPI-147 appears to be more flexible than IPI-725. Although both γ-turns contain the same residues, their orders in the turn are reversed. The β-turn in IPI-725 is formed with d -Val:Leu:d -Trp:d -Asp, while in IPI-147, the β-turn is formed with d -Asp:Trp:d -Leu:d -val. The activities and solution conformations of IPI-147 and IPI-725 were also compared with BQ-123 [Cyclo(d -Trp-d -Asp-Pro-d -Val-Leu)], a well characterized, highly potent endothelin antagonist. © Munksgaard 1996.     

槲皮素对培养内皮细胞产生和释放内皮素和环磷酸鸟苷的影响

槲皮素对培养内皮细胞产生和释放内皮素和环磷酸鸟苷的影响赵雪英，顾振纶（苏州医学院药理学教研室，苏州２１５００７，中国）关键词槲皮素；脐静脉；血管内皮；培养的细胞；凝血酶；血小板；内皮素；环鸟苷一磷酸目的：研究槲皮素（Ｑｕｅ）对不同状态下的内皮细胞形成...     

麻黄素衍生物对豚鼠心肌细胞内cAMP含量的影响

采用环磷酸腺苷（ｃＡＭＰ）蛋白质结合测定法，测定零浓度，最小浓度，半数有效量（ＥＤ５０）浓度和最大浓度的异丙肾上腺素，去甲伪麻黄素，普萘洛尔，甲基麻黄素对心肌细胞内ｃＡＭＰ含量的影响，结果看到随着异丙肾上腺素，去甲伪麻黄素浓度的增大，心肌细胞内ｃＡＭＰ的含量增加。以量－效曲线中求得的ＥＤ５０浓度对ｃＡＭＰ含量的影响最明显，去甲伪麻黄素对ｃＡＭＰ含量的影响是异丙肾上腺素的４７３％±０１８，随着普萘洛尔，甲基麻黄素浓度的增大，心肌细胞内ｃＡＭＰ含量逐渐减少，在最大浓度时达到最大抑制，甲基麻黄素对ｃＡＭＰ含量的影响是普萘洛尔的３８３％±０２。结果进一步证明，甲基麻黄素在一定浓度范围内具有β－受体阻滞剂的特性。     

反复性脑缺血致大鼠大脑皮质损伤与cAMP、SOD及MDA含量的变化

本实验动态对比观察单次性15mim和反复性3×5min大鼠全脑缺血/再灌流,大脑皮质cAMP、SOD和MDA含量的变化及相应的病理改变、发现反复性脑缺血及再灌流早期cAMP含量明显增高,SOD活性显著降低,MDA则延迟性持续显著增高;反复性缺血组皮质神经元损害显著重于单次缺血组。结果提示cAMP和自由基均可能参与了反复性脑缺血神经元损害的病生机制。