节节麦和黑麦杂种胚再生植株的分子细胞遗传学分析

利用杂种幼胚愈伤组织诱导和再生技术产生了节节麦和黑麦杂种幼胚无性系.胚拯救直接成苗植株、继代培养60d的再生植株和继代培养420d的再生杂种植株PMCs减数分裂MI染色体构型分别为10.82I+1.57II+0.01III,9.96I+1.59II+0.25III+0.03IV,7.59Ⅰ+3.10Ⅱ+0.05Ⅲ+0.01IV.继代培养420d左右胚再生无性系其减数分裂MI染色体配对频率大幅度提高,利用原位杂交技术分析表明其染色体配对频率提高和染色体结构和数量变异无关.提示体细胞无性系变异可能是增加部分同源染色体配对,增加属间种基因交流的一个新途径.     

GTP-binding proteins couple cardiac muscarinic receptors to a K channel

Binding of acetylcholine (ACh) to cardiac muscarinic ACh receptors (mAChR) activates a potassium channel that slows pacemaker activity. Although the time course of this activation suggests a multi-step process with intrinsic delays of 30-100 ms, no second-messenger system has been demonstrated to link the mAChR to the channel. Changes in cyclic nucleotide levels (cyclic AMP and cyclic GMP) do not affect this K channel or its response to muscarinic agonists. Indeed, electrophysiological experiments argue against the involvement of any second messenger that diffuses through the cytoplasm. We report here that coupling of the mAChR in embryonic chick atrial cells to this inward rectifying K channel requires intracellular GTP. Furthermore, pretreatment of cells with IAP (islet-activating protein from the bacterium Bordetella pertussis) eliminates the ACh-induced inward rectification. As IAP specifically ADP-ribosylates two GTP-binding proteins, Ni and No, that can interact with mAChRs, we conclude that a guanyl nucleotide-binding protein couples ACh binding to channel activation. This represents the first demonstration that a GTP-binding protein can regulate the function of an ionic channel without acting through cyclic nucleotide second messengers.     

Characterization of 64-, 123- and 182-base-pair exons in the mouse alpha 2(IV) collagen gene

Genes encoding types I, II and III collagens (fibrillar collagens) contain many discrete-size exons, most of them 54 base pairs (bp) long, in addition to the 45-, 99-, 108- and 162-bp exons. It has been suggested that these collagen genes evolved from an ancestral coding unit of 54 bp. Type IV collagen is a specific component of basement membranes and contains two genetically distinct polypeptides, the alpha 1(IV) and alpha 2(IV) chains. It differs from the types I-III collagens in that it contains interruptions in the Gly-X-Y repeat sequence and does not form ordered fibrillar structures. We have isolated complementary DNA and genomic clones for the mouse alpha 2(IV) collagen chain and here characterize 64-, 123- and 182-bp exons in the Gly-X-Y coding domain of the gene. The data suggest that the alpha 2(IV) collagen gene may have evolved differently from those encoding the fibrillar collagens.     

Uncoupling of cardiac muscarinic and beta-adrenergic receptors from ion channels by a guanine nucleotide analogue

Guanine nucleotide binding proteins, interchangeably called N or G proteins, seem to be the primary signal-transducing components of various agonist-induced cell membrane functions. In the heart, G proteins have been implicated in beta-adrenergic modulation of the slow inward Ca2+ current. We have investigated the role of G proteins in muscarinic activation of an inwardly rectifying, acetylcholine (ACh)-induced K+ current (IACh), and beta-adrenergic activation of an (isoprenaline)-induced Ca2+ current (Isi). Here we report that intracellular application of the non-hydrolysable GTP analogue 5'-guanylylimidodiphosphate (GppNHp) brought about an agonist-induced, antagonist-resistant, persistent activation of IACh and Isi. This functional uncoupling of channel from receptor suggests that the muscarinic receptor and the IACh channel are separate molecular structures. Membrane conductance responses to sequential activation of muscarinic and beta-adrenergic receptors demonstrate that in contrast to the muscarinic inhibition of Isi, muscarinic stimulation of IACh is mediated by a G protein via a pathway that does not involve adenylate cyclase. Taken together, the results support the notion that agonist is required to induce GppNHp binding and/or activation of the G proteins. Once triggered by agonist, the control system remains maximally activated, thereby transforming the cell so that it no longer responds to subsequent homologous receptor-mediated signals.     

产生苝醌类化合物真菌的化学成分及光敏活性研究

 研究菌寄生菌属真菌(Ascomycetes Hypocreaceae Hypomyces(Fr.)Tul.sp.)菌丝体的化学成分.用丙酮回流提取,用二氯甲烷和甲醇洗脱,硅胶H柱层析分离,化学与波谱学进行结构鉴定.从菌丝体中分离得4个化合物,分别鉴定为甘露醇(I),痂囊腔菌素A(II),竹红菌甲素(III)和竹红菌乙素(IV).用微生物纸片法测定了化合物II,III,IV的光敏活性.     

Coiled-coil fibrous domains mediate ligand binding by macrophage scavenger receptor type II

The macrophage scavenger receptor, which has been implicated in the pathogenesis of atherosclerosis, has an unusually broad binding specificity. Ligands include modified low-density lipoprotein and some polyanions (for example, poly(I) but not poly(C]. The scavenger receptor type I (ref. 3) has three principal extracellular domains that could participate in ligand binding: two fibrous coiled-coil domains (alpha-helical coiled-coil domain IV and collagen-like domain V), and the 110-amino-acid cysteine-rich C-terminal domain VI. We have cloned complementary DNAs encoding a second scavenger receptor which we have termed type II. This receptor is identical to the type I receptor, except that the cysteine-rich domain is replaced by a six-residue C terminus. Despite this truncation, the type II receptor mediates endocytosis of chemically modified low-density lipoprotein with high affinity and specificity, similar to that of the type I receptor. Therefore one or both of the extracellular fibrous domains are responsible for the unusual ligand-binding specificity of the receptor.     

Cloning and sequence analysis of cDNAs encoding two distinct somatostatin precursors found in the endocrine pancreas of anglerfish

Complementary DNAs for two distinct anglerfish somatostatin peptides (termed I and II) have been cloned in bacterial plasmids and sequenced. The nucleotide sequence for somatostatin I encodes a large percursor peptide (molecular weight 13,300) in which the somatostatin hormones is at the carboxyl terminus. The predicted 14-amino acid sequence for anglerfish somatostatin I is the same as mammalian somatostatin. Somatostatin II is also synthesized as part of a larger precursor (molecular weight 14,100) with the presumptive somatostatin hormone also at the carboxyl terminus. The 14-amino acid sequence of somatostatin II differs from somatostatin I at two internal residues (Tyr in place of Phe 7 and Gly in place of Thr 10). The two different somatostatins may have distinct biological activities. Homologies in the amino acid sequences of the two peptides outside the somatostatin moiety suggest other regions of the molecules have biological functions.     

Existence of distinct sodium channel messenger RNAs in rat brain

The sodium channel is a voltage-gated ionic channel essential for the generation of action potentials. It has been reported that the sodium channels purified from the electric organ of Electrophorus electricus (electric eel) and from chick cardiac muscle consist of a single polypeptide of relative molecular mass (Mr) approximately 260,000 (260K), whereas those purified from rat brain and skeletal muscle contain, in addition to the large polypeptide, two or three smaller polypeptides of Mr 37-45K. Recently, we have elucidated the primary structure of the Electrophorus sodium channel by cloning and sequencing the DNA complementary to its messenger RNA. Despite the apparent homogeneity of the purified sodium channel preparations, several types of tetrodotoxin (or saxitoxin) binding sites or sodium currents have been observed in many excitable membranes. The occurrence of distinguishable populations of sodium channels may be attributable to different states of the same channel protein or to distinct channel proteins. We have now isolated complementary DNA clones derived from two distinct rat brain mRNAs encoding sodium channel large polypeptides and present here the complete amino-acid sequences of the two polypeptides (designated sodium channels I and II), as deduced from the cDNA sequences. A partial DNA sequence complementary to a third homologous mRNA from rat brain has also been cloned.     

Acetylcholine analogue stimulates DNA synthesis in brain-derived cells via specific muscarinic receptor subtypes

Little is known about the factors which regulate the growth and development of the mammalian brain. Although proliferation of neuronal cells ceases relatively early in development, certain types of glial cells proliferate and differentiate mainly perinatally. In the perinatal period, the ability of acetylcholine to stimulate phosphoinositide (PI) hydrolysis in brain reaches peak levels, and indeed the stable acetylcholine analogue carbachol can stimulate PI hydrolysis of primary neonatal astroglial cells. As PI hydrolysis is thought to be important in the regulation of cell proliferation, we investigated whether cellular DNA synthesis can be induced by carbachol. Our results show that carbachol stimulates DNA synthesis via muscarinic acetylcholine receptors (mAChRs), in primary astrocytes derived from perinatal rat brain, in an age-dependent fashion. Carbachol is also mitogenic in certain brain-derived astrocytoma and neuroblastoma cell lines, as well as in chinese hamster ovary (CHO) cells expressing recombinant muscarinic receptors. DNA synthesis is strongly activated by carbachol in those brain-derived cell lines and transfected CHO cells that express mAChR subtypes which activate PI hydrolysis efficiently, and poorly activated in cells expressing mAChR subtypes which only weakly activate PI hydrolysis. These results strongly support a role for acetylcholine in regulating astroglial cell growth in the developing brain, and indicate that the specificity of acetylcholine-induced cell proliferation may be determined by the expression of those mAChR subtypes which activate PI hydrolysis.     

The G protein-gated atrial K+ channel is stimulated by three distinct Gi alpha-subunits

The guanine nucleotide-binding protein, Gi, which inhibits adenylyl cyclase, has recently been shown to have three subtypes of the alpha-subunit, termed Gi alpha-1, Gi alpha-2 and Gi alpha-3. They share 87-94% amino-acid sequence homology and so are difficult to separate from one another. Among other functions, purified preparations activate K+ channels but there is confusion over which of the subtypes activates the muscarinic K+ channels of the atrial muscle of the heart: Gi alpha-3, also termed Gk, has been shown to activate this channel but it is not clear whether Gi alpha-1 does or does not. To clarify this problem, we expressed the subtypes separately in Escherichia coli to eliminate contamination by other subtypes and tested the recombinant alpha- chains on atrial muscarinic K+ channels. Although we anticipated that only Gi alpha-3 would have Gk activity, to our surprise all three recombinant subtypes were active, from which we deduce that the Gi subtypes are multifunctional.     

蕨菜黄酮饲喂肉鸡的试验研究

试验研究了不同水平的蕨菜黄酮对肉鸡的采食量、日增重、料重比等的影响。试验选用日龄相同、健康肉雏鸡80只,随机分成四组,每组20只,在其他条件完全相同的情况下,试验Ⅰ、Ⅱ、Ⅲ组基础日粮中分别添加50mg/kg.d、100mg/kg.d、150mg/kg.d的蕨菜黄酮,对照组Ⅳ只饲喂基础日粮。结果表明:蕨菜黄酮可提高肉鸡的采食量、平均日增重,降低料重比。     

Evidence for the T3-associated 90K heterodimer as the T-cell antigen receptor

Several surface molecules appear to be involved in antigen recognition by human T lymphocytes including the monomorphic 20/25K T3 structure present on all mature T lymphocytes and the subset-specific associative recognition elements, T4 and T8 (refs 1-8). More recently, Ti1, a clonally unique antigen recognition structure comprised of a 49,000 molecular weight (49K) alpha-chain and a 43K beta-chain, linked to T3 was identified on a major histocompatibility complex (MHC) class I specific T8+ T-cell clone, CT8III (ref. 9). To determine whether analogous receptor molecules could be found on other T-cell clones of differing specificity, we produced monoclonal antibodies against a clonal structure (Ti2) on an MHC class II specific T4+ lymphocyte, CT4II, derived from the same donor as CT8III. The Ti2 structure on CT4II is shown here to be a disulphide-linked heterodimer like Ti1 on CT8III and is composed of subunits of similar molecular weight. Monoclonal antibodies against Ti2 or Ti1 block antigen specific functions of the respective clone without showing any cross-reactivity. These findings suggest that each T lymphocyte, regardless of subset derivation or specificity, uses an analogous Ti heterodimer for antigen specific function. The latter is linked to T3 and expressed on the cell surface at an identical density (30,000-40,000 sites per cell).     

水线草的化学成分

采用硅胶柱色谱、凝胶柱色谱、重结晶等方法对水线草的化学成分进行了分离和纯化,并根据其理化性质和波谱数据鉴定了化合物的结构,结果显示,从水线草中可分离得到7个化合物,分别鉴定为：5,6,7,4’-四甲氧基黄酮（I）,7-羟基-5,6,4’-三甲氧基黄酮（Ⅱ）,3’,4’,5,6,7-五甲氧基黄酮（Ⅲ）,5,7,4’-三羟基-6-甲氧基黄酮（IV）,5,4’-二羟基-6,7-二甲氧基黄酮（V）,α-香树精（Ⅵ）,β-谷甾醇（Ⅶ）,这些化合物是首次从该种植物中分离得到的．     

Drosophila melanogaster mitochondrial DNA, a novel organization and genetic code

The sequence of a 4,869 base-pair fragment of Drosophila melanogaster mitochondrial DNA is presented. It contains genes for cytochrome oxidase subunits I, II and III, ATPase subunit 6 and six tRNAs together with two unassigned reading frames. The gene organization differs from that of mammalian mitochondrial DNAs. Evidence is provided for a genetic code in which AGA codes for serine and the quadruplet ATAA is used in initiation of translation.     

石菖蒲化学成分研究

为研究石菖蒲根茎部位的化学成分,利用系统溶剂提取法、正相和反相硅胶柱色谱法、半制备型高效液相色谱法进行了分离和纯化,并采用NMR谱学技术进行结构鉴定,最后得到5种化合物,分别鉴定为顺式甲基异丁香酚(化合物Ⅰ),细辛醛(化合物Ⅱ),苯甲酸(化合物Ⅲ),豆甾醇(化合物Ⅳ),菖蒲醇酮(化合物Ⅴ),且化合物Ⅲ为首次从该植物中分离而得.为深入研究石菖蒲提供了理论依据.     

博落回生物碱成分及其抗菌活性的研究

为研究罂粟科植物博落回的生物碱成分,采用硅胶柱层析、重结晶等方法对其进行了分离纯化,结果获得了5个生物碱,分别经波谱分析鉴定为:原阿片碱(I),pancorine(II),去甲基白屈菜红碱(III),6-丙酮基二氢血根碱(IV),6-丙酮基二氢白屈菜红碱(V),其中化合物(II)为首次从该植物中分离得到.抗菌圈检测发现博落回总生物碱抗菌作用较强,对金黄色葡萄球菌的抑制作用尤为显著.     

乳腺癌患者细胞免疫指标的检测及意义

目的检测乳腺癌患者外周血T淋巴细胞总数及CD4~+T细胞、CD8~+T细胞、CD45RA~+T细胞、CD45RO~+T细胞等T淋巴细胞亚群的百分率,用以评价患者的免疫状态.方法选择女性原发性乳腺肿瘤患者50例为病例组,并以病理检查的TNM分期结果做进一步分组,其中乳腺癌Ⅰ期27例,乳腺癌Ⅱ+Ⅲ期23例;选择女性健康体检者40例为健康对照组.应用流式细胞仪,分别检测各组外周血T淋巴细胞亚群的数量,统计分析各组检测结果的差异性.结果乳腺癌Ⅱ+Ⅲ期组CD3~+T细胞和CD4~+T细胞百分率明显低于正常对照组和乳腺癌Ⅰ期组,差异具有统计学意义(P0.05);乳腺癌Ⅰ期组CD45RA~+T细胞明显低于正常对照组,乳腺癌Ⅱ+Ⅲ期组CD45RA~+T细胞明显低于乳腺癌Ⅰ期组,差异具有统计学意义(P0.05);乳腺癌Ⅰ期组CD45RO~+T细胞明显高于正常对照组,乳腺癌Ⅱ+Ⅲ期组CD45RO~+T细胞明显高于乳腺癌Ⅰ期组,差异具有统计学意义(P0.05).结论T细胞亚群检测是评价肿瘤患者细胞免疫功能的重要指标,具有重要的临床应用价值.乳腺癌患者免疫功能与肿瘤恶变的发生、发展、临床分期有一定相关性,随着病情的进展,机体免疫功能呈现下降趋势.     

Structure and dynamics of the M3 muscarinic acetylcholine receptor

Acetylcholine, the first neurotransmitter to be identified, exerts many of its physiological actions via activation of a family of G-protein-coupled receptors (GPCRs) known as muscarinic acetylcholine receptors (mAChRs). Although the five mAChR subtypes (M1-M5) share a high degree of sequence homology, they show pronounced differences in G-protein coupling preference and the physiological responses they mediate. Unfortunately, despite decades of effort, no therapeutic agents endowed with clear mAChR subtype selectivity have been developed to exploit these differences. We describe here the structure of the G(q/11)-coupled M3 mAChR ('M3 receptor', from rat) bound to the bronchodilator drug tiotropium and identify the binding mode for this clinically important drug. This structure, together with that of the G(i/o)-coupled M2 receptor, offers possibilities for the design of mAChR subtype-selective ligands. Importantly, the M3 receptor structure allows a structural comparison between two members of a mammalian GPCR subfamily displaying different G-protein coupling selectivities. Furthermore, molecular dynamics simulations suggest that tiotropium binds transiently to an allosteric site en route to the binding pocket of both receptors. These simulations offer a structural view of an allosteric binding mode for an orthosteric GPCR ligand and provide additional opportunities for the design of ligands with different affinities or binding kinetics for different mAChR subtypes. Our findings not only offer insights into the structure and function of one of the most important GPCR families, but may also facilitate the design of improved therapeutics targeting these critical receptors.