多胺的生殖生物学作用及其研究进展

多胺是一类聚阳离子化合物，包括精胺、亚精胺和腐胺等。哺乳动物体内多胺来源于氨基酸合成或从饮食中摄取，多胺能够清除细胞内过多的活性氧簇（ROS），调节其氧化应激水平。多胺在雄性和雌性的生殖过程和胚胎/胎儿发育中起重要作用。研究发现，多胺参与调节细胞生长和基因表达，且与有丝分裂、减数分裂有关。在雄性，多胺与精子生成相关，并调节精子活性；在雌性，多胺与卵泡发育及排卵有关，且参与调节类固醇激素生成。在体外成熟（IVM）中外源性添加多胺，可有效地减少卵母细胞非整倍体率并且改善其胚胎发育。此外，多胺缺乏会导致胚胎发育停滞。多胺参与胎盘发育以及在胎儿发育过程中母婴的物质交换。综述多胺生物学功能及其对配子发生及胎盘发育的作用。     

The putative polyamine antagonists ifenprodil and SL 82.0715 enhance dopamine efflux from rat striatal slices independent of NMDA receptor activation

NMDA stimulated the release of endogenous or tritiated dopamine from rat striatal slices and tritiated norepinephrine from cortical and hippocampal slices. The putative polyamine antagonists ifenprodil and SL 82.0715 inhibited [³H]norepinephrine release from cortical and hippocampal slices but enhanced the basal efflux of endogenous and tritiated dopamine from striatal slices. Incubation of striatal slices in a calcium-free buffer did not ameliorate these effects suggesting that the increase in dopamine efflux was not due to a calcium-dependent release process. Superfusion of striatal slices with 10 μM of either ifenprodil, cocaine, or amphetamine resulted in a significant release of tritiated dopamine which was reversed when the slices were again superfused with non-drug-containing buffer. The release observed in the presence of 10 μM ifenprodil (7-fold increase over basal) was intermediate between that observed for cocaine (3-fold increase) and amphetamine (12-fold increase). Both ifenprodil and SL 82.0715 also blocked the uptake of [³H]dopamine into striatal synaptosomes with IC₅₀ values of approximately 1.5 μM. This was again intermediate between the values obtained for cocaine (0.43 μM) and amphetamine (4.2 μM). These results suggest that ifenprodil and its analog SL 82.0715 may act as indirect dopamine agonists by both blocking presynaptic dopamine uptake and by directly increasing the basal efflux of dopamine.     

1,4,7,10,13,16-六氮杂环十八烷及其 Pd~(2 )Cr~(3 )配位化合物的IR、UV和NMR光谱学研究

作者对１，４，７，１０，１３，１６－六氮杂环十八烷（［１８］ａｎｅＮ６）及其Ｐｄ２＋、Ｃｒ３＋ 配位化合物［Ｐｄ２（［１８］ａｎｅＮ６）Ｂｒ２］Ｂｒ２· ４Ｈ２Ｏ、［Ｃｒ（［１８］ａｎｅＮ６）］Ｂｒ３进行了红外、紫外 和核磁共振光谱学研究。红外图谱中与Ｐｄ２＋、Ｃｒ３＋配位化合物Ｐｄ－Ｎ、Ｃｒ－Ｎ配位键伸 缩振动相对应的谱峰位置分别为 ５０２ ｃｍ－１和 ４９２ｃｍ－１。认为 Ｐｄ２＋配位化合物水溶液 在 ３５４ ｎｍ（ε＝１４１４）处和Ｃｒ３＋配位化合物水溶液在 ４６７． ２ ｎｍ（ε＝２２０）、３６６． ２ｎｍ（ε ＝８０）处的紫外吸收为中心离子Ｐｄ２＋、Ｃｒ３＋的电子ｄ轨道ｄ－ｄ能级跃迁所致。     

Stimulation of clonal tumor cell growth in vitro by inhibiting the serum polyamine oxidase activity

Summary Several tumors are characterized by elevated levels of polyamines involved in vital cell proliferation processes. Polyamine oxidases (PAO), present in ruminant and particularily in fetal calf serum (FCS), degrade polyamines to polyaminoaldehydes and other products that inhibit cell proliferation. Since most in vitro assays for cloning tumor stem cells use FCS as an essential supplement of the nutrient media, we examined the effects of specifically inhibiting the PAO activity on the clonal growth of leukemic cells and the following normal lymphocytes: the W 25 rat chloroleukemia, the M1 mouse myeloblastic and the L 1210 rat lymphoblastic leukemia, a primary human acute myeloblastic leukemia (AML) and acute lymphocytic leukemia (ALL) as well as normal human PHA-stimulated lymphocytes. In the presence od horse serum, nontoxic doses of the PAO inhibitor 1-hydroxybenzyloxyamine did not affect colony growth of either cell type. However, in the presence of FCS, clonal growth of W 25, ALL, AML, and PHA lymphocytes was significantly stimulated by the enzyme inhibitor. Our data suggest (a) that poor cell proliferation of several tumors in vitro may result from the reaction of polyamines (from cells) and PAO (from serum), (b) that this can be easily tested by means of a specific PAO inhibitor, and (c) that the growth conditions can be optimized by adding nontoxic doses of the enzyme inhibitor or by exchanging FCS for another serum.     

Ornithine decarboxylase activity in the isolated perfused rat heart.

Ornithine decarboxylase activity in rat hearts perfused by the Langendorff technique decreased by 50% after 1 h. Pyridoxal-5-phosphate, amino acids, cycloheximide, isoprenaline and insulin, when added to the perfusion medium, did not significantly affect myocardial ornithine decarboxylase activity. Growth hormone, T₃ and dibutyryl 3′,5′-cAMP were each able to prevent a loss of enzyme activity in hearts perfused for 1 h. When both T₃ and cycloheximide were added to the perfusion medium the ornithine decarboxylase activity was similar to that of hearts perfused with a medium containing T₃ alone. The results suggested that the biosynthesis of ornithine decarboxylase stopped with the onset of perfusion. The elevated enzyme activity after perfusion with growth hormone, T₃ or dibutyryl 3′,5′-cAMP was probably due to a decreased degradation of the enzyme protein.     

Inhibition of murine embryonic development by α-difluoromethylornithine,an irreversible inhibitor of ornithine decarboxylase

The activities of ornithine decarboxylase (ODC) and S-adenosyl-L-methionine decarboxylase (SAMDC) and the concentrations of putrescine, spermidine and spermine were measured in mouse uterus, placenta and foetus during gestation. The prominent post-implantation biochemical changes in the intact uterus were associated mainly with the deciduomata and significant ODC activity was located in theembryo. Administration of the irreversible inhibitor of ODC, α-difluoromethylornithine, DFMO, 2% in the drinking water during days 5–8 of gestation, abolished the increases in uterine ODC activity, putrescine and spermidine concentrations and enhanced the activity of SAMDC. Treated animals showed no signs of pregnancy when autopsied on day 18. The alterations in deciduomal weight and the changes in uterine DNA, RNA and protein content indicated that decidualization following DFMO took place normally but that embryonic growth was arrested. Treatment on single days with DFMO, 200 mg/kg every six h, revealed optimal contragestational effects on day 8 which corresponded exactly to the time of the peak in deciduomal ODC activity. Treatment with DFMO at times other than during the vulnerable period of days 5–8 has less prominent effects on gestation. An increase in ODC activity appears to be an essential factor during a short, but critical, period after implantation for continued murine embryonal growth.     

高效液相色谱法快速测定脑梗塞模型大鼠脑组织中多胺的含量

目的:建立一种简便、灵敏和快速分离测定大鼠脑组织中腐胺、精脒和精胺等多胺含量的高效液相色谱法。方法:采用苯甲酰氯作为衍生化试剂,以1,6-己二胺为内标,采用polygocyl(250×4.6 mm 5μm)C18色谱柱,流动相为甲醇-水(62:38 V/V),流速1.0 mL/min,检测波长229 nm。结果:本法线性范围是1～2 000/mL,回收率大于90%。日内和日间变异系数为1.5%～4.2%。最低定量浓度为1 nmol/mL。结论:该方法符合生物样品分析要求,为脑组织中多胺的含量测定提供了一种简便、准确、灵敏度高的分析方法。     

Epigenetic regulation of spermidine/spermine N1-acetyltransferase (SAT1) in suicide

We have recently shown that the expression of spermidine/spermine N1-acetyltransferase (SAT1) is downregulated across the brains of suicide completers, and that its expression is influenced by genetic variations in the promoter. Several promoter polymorphisms in SAT1, including rs6526342, have been associated with suicide and other psychiatric disorders, and display haplotype-specific effects on expression. However, these effects cannot explain total variability in SAT1 expression, and other regulatory mechanisms, such as epigenetic factors, may also be at play. In this study, we assessed the involvement of epigenetic factors in controlling SAT1 expression in the prefrontal cortex of suicide completers by mapping CpG methylation across a 1880-bp region of the SAT1 promoter, and measuring levels of tri-methylated histone-3-lysine 27 (H3K27me3) at the promoter in suicide completers and controls. Our results demonstrated that CpG methylation was significantly negatively correlated with SAT1 expression. Although overall or site-specific CpG methylation was not associated with suicide or SAT1 expression, we observed high levels of methylation at the polymorphic CpG site created by rs6526342, indicating a relationship between promoter haplotypes and methylation. There was no association between H3K27me3 and suicide, nor was this modification associated with SAT1 expression. Overall, our results indicate that epigenetic factors in the promoter region of SAT1 influence gene expression levels, and may provide a mechanism for both our previous findings of haplotype-specific effects of promoter variations on SAT1 expression, as well as the widespread downregulation of SAT1 expression observed in the brains of suicide completers.     

Polyamines as a defense mechanism against lipoperoxidation in Trypanosoma cruzi

The polyamines, spermine and spermidine--organic polycations that are absolutely required for eukaryotic cell growth--are shown here to function in Trypanosoma cruzi epimastigotes, as protectors of membrane lipoperoxidation by reactive oxygen species generated either by H2O2/Fe2+ or nifurtimox. In vitro, spermine and spermidine inhibited lipoperoxidation in a dose dependent manner. Spermine was more efficient than spermidine in its inhibitory effect. Lipid peroxidation induced by H2O2 showed an IC50 of 0.55 mM for spermine and 0.9 mM for spermidine while an IC50 of 0.8 mM for spermine and 1.5 mM for spermidine were observed when lipoperoxidation was elicited by nifurtimox. Likewise in vivo, both exogenously added spermine and spermidine or endogenous increase of spermine levels induced by phorbol ester, protected against lipoperoxidation and decreased citotoxicity provoked by nifurtimox. Putrescine and cadaverine, also present in T. cruzi had no effect at all. None of the polyamines had any effect neither on the scavenging of superoxide anion nor on the regulation of antioxidant enzymes such as superoxide dismutase and peroxidases involved in H2O2 detoxification. Here we point out that spermine, by acting as a protector of membrane lipoperoxidation might contribute to survival of T. cruzi continuously exposed to oxidative stress.