萌发花生种子子叶肽链内切酶的纯化和性质

萌发花生种子子叶的肽链内切酶经硫酸铵沉淀,ＳｅｐｈａｄｅｘＧ－１００凝胶层析,ＤＥＡＥ－纤维素２３阴离子交换层析和ＤＥＡＥ－ＳｅｐｈａｄｅｘＡ５０层析,得到纯化的酶,该酶有两条同工酶,分子量分别为５８和５５ＫＤ,Ｋｍ为９．９μｍｏｌ／Ｌ,是半胱氨型肽链内切酶（ＥＣ３．４．２２）,对未萌发花生种子的贮藏蛋白没有明显降解作用．     

Novel nuclear ribonucleoprotein structural components in the dormouse adrenal cortex during hibernation

Adrenocortical cell nuclei of the dormouse Muscardinus avellanarius were investigated by electron microscopic immunocytochemistry in hibernating, arousing and euthermic individuals. While the basic structural constituents of the cell nucleus did not significantly were found in nuclei of hibernating dormice. Lattice-like bodies (LBs), clustered granules (CGs), fibrogranular material (FGM) and granules associated with bundles of nucleoplasmic fibrils (NF) all contained ribonucleoproteins (RNPs), as shown by labeling with anti-snRNP (small nuclear RNP), anti-m₃G-capped RNA and anti-hnRNP (heterogeneous nuclear RNP) antibodies. Moreover, the FGM also showed immunoreactivity for the proliferation associated nuclear antigen (PANA) and the non-snRNP splicing factor SC-35. All these nuclear structural components disappeared early during arousal and were not found in euthermic animals. These novel RNP-containing structures, which have not been observed in other tissues investigated so far in the same animal model, could represent storage and/or processing sites for pre-mRNA during the extreme metabolic condition of hibernation, to be quickly released upon arousal. NFs, which had been sometimes found devoid of associated granules in nuclei of brown adipose tissue from hibernating dormice, were present in much higher amouts in adrenocortical cell nuclei; they do not contain RNPs and their role remains to be elucidated. The possible roles of these structures are discussed in the frame of current knowledge of morpho-functional relationships in the cell nucleus.     

Angiotensin II Receptor Type I-Regulated Anion Secretion in Cystic Fibrosis Pancreatic Duct Cells

The β-adrenergic (cAMP-dependent) regulation of Cl⁻ conductance is defective in cystic fibrosis (CF). The present study explored alternative regulation of anion secretion in CF pancreatic ductal cells (CFPAC-1) by angiotensin II (AII) using the short-circuit current (I _SC ) technique. An increase in I _SC could be induced in CFPAC-1 cells by basolateral or apical application of AII in a concentration-dependent manner (EC₅₀ at 3 μm and 100 nm, respectively). Angiotensin receptor subtypes were identified using specific antagonists, losartan and PD123177, for AT₁ and AT₂ receptors, respectively. It was found that losartan (1 μm) could completely inhibit the AII-induced I _SC , whereas, PD123177 exerted insignificant effect on the I _SC , indicating predominant involvement of AT₁ receptors. The presence of AT₁ receptors in CFPAC-1 cells was also demonstrated by immunohistochemical studies using specific antibodies against AT₁ receptors. Confocal microscopic study demonstrated a rise in intracellular Ca²⁺ upon stimulation by AII indicating a role of intracellular Ca²⁺ in mediating the AII response. Depletion of intracellular but not extracellular pool of Ca²⁺ diminished the AII-induced I _SC . Treatment of the monolayers with a Cl⁻ channel blocker, DIDS, markedly reduced the I _SC , indicating that a large portion of the AII-activated I _SC was Cl⁻-dependent. AII-induced I _SC was also observed in monolayers whose basolateral membranes had been permeabilized by nystatin, suggesting that the I _SC was mediated by apical Cl⁻ channels. Our study indicates an AT₁-mediated Ca²⁺-dependent regulatory mechanism for anion secretion in CF pancreatic duct cells which may be important for the physiology and pathophysiology of the pancreas. Received: 17 June 1996/Revised: 14 November 1996     

银杏速生早实示范栽培试验

本研究是在我区银杏主产区兴安进行的８０多亩,３０００多株的示范栽培试验。其综合技术措施是选用良种嫁接苗、适当密植、配置雄株、整形修剪、合理施肥、防治病虫害及促花早实等。种后５—６年取得速生、早实、高产的良好效果。     

基因转移与肿瘤基因工程疫苗

综述了近年来有关利用基因转移技术修饰肿瘤细胞制备肿瘤基因工程疫苗的最新研究进展,着重阐述了逆转录病毒载体介导的基因转移及其安全性;归纳了目前可用于肿瘤基因工程疫苗的各种目的基因的特点及作用并对这类肿瘤疫苗制备过程中所存在的问题进行了分析.     

溶剂极性及盐酸胍对碳酸酐酶构象的影响

以紫外荧光光谱为检测手段,比较研究了溶剂极性及盐酸胍对碳酸酐酶构象的影响,结果表明,当盐酸胍浓度小于１ｍｏｌ／Ｌ时酶呈天然构象,１．５ｍｏｌ／Ｌ－２．０ｍｏｌ／Ｌ的盐酸胍导致该酶呈伸展构象;而乙醇不以导致该酶产生稳定的中间态构象,１ｍｏｌ／Ｌ和３ｍｏｌ／Ｌ的甲醇以及３ｍｏｌ／Ｌ的乙醇对盐酸胍致碳酸酐酶中间态的影响不大,甲醇略使致中间态的盐酸胍浓度下降,乙醇略使之上升。     

Thiophosphorylation of (Na + K+)-ATPase yields an ADP-sensitive phosphointermediate

(1) Treatment of $\text{(Na}{}^{\mathrm{+}}\text{+ K}{}^{\mathrm{+}}\text{)-ATPase}$ from rabbit kidney outer medulla with the $\text{γ-}{}^{35}\text{S}$ labeled thio-analogue of ATP in the presence of $\text{Na}{}^{\mathrm{+}}\text{+ Mg}{}^{\mathrm{2+}}$ and the absence of K⁺ leads to thiophosphorylation of the enzyme. The $\text{K}{}_{\mathrm{<mtext>m</mtext>}}$ value for [γ-S]ATP is 2.2 μM and for Na⁺ 4.2 mM at 22°C. Thiophosphorylation is a sigmoidal function of the Na⁺ concentration, yielding a Hill coefficient $\text{n}\text{H}\text{= 2.6}$. (2) The thio-analogue ($\text{K}{}_{\mathrm{<mtext>m</mtext><mtext>\; =\; 35\; \mu M</mtext>}}$) can also support overall $\text{(Na}{}^{\mathrm{+}}\text{+ K}{}^{\mathrm{+}}\text{)-ATPase}$ activity, but $\text{V}{}_{\mathrm{<mtext>max</mtext>}}$ at 37°C is only $\text{1.3 γ}\text{mol}\text{· (mg protein)}{}^{\mathrm{?}}\text{·}$ h^?1 or 0.09% of the specific activity for ATP ($\text{K}{}_{\mathrm{<mtext>m</mtext><mtext>\; =\; 0.43\; mM</mtext>}}$). (3) The thiophosphoenzyme intermediate, like the natural phosphoenzyme, is sensitive to hydroxylamine, indicating that it also is an acylphosphate. However, the thiophosphoenzyme, unlike the phosphoenzyme, is acid labile at temperatures as low as 0°C. The acid-denatured thiophosphoenzyme has optimal stability at pH 5–6. (4) The thiophosphorylation capacity of the enzyme is equal to its phosphorylation capacity, indicating the same number of sites. Phosphorylation by ATP excludes thiophosphorylation, suggesting that the two substrates compete for the same phosphorylation site. (5) The (apparent) rate constants of thiophosphorylation (0.4 s^?1 vs. 180 s^?1), spontaneous dethiophosphorylation (0.04 s^?1 vs. 0.5 s^?1) and K⁺-stimulated dethiophosphorylation (0.54 s^?1 vs. 230 s^?1) are much lower than those for the corresponding reactions based on ATP. (6) In contrast to the phosphoenzyme, the thiophosphoenzyme is ADP-sensitive (with an apparent rate constant in ADP-induced dethiophosphorylation of 0.35 s^?1, $\text{K}{}_{\mathrm{<mtext>m</mtext>}}$$\text{ADP = 48 μM at 0.1 mM ATP}$) and is relatively K⁺-insensitve. The $\text{K}{}_{\mathrm{<mtext>m</mtext>}}$ for K⁺ in dethiophosphorylation is 0.9 mM and in dephosphorylation 0.09 mM. The thiophosphoenzyme appears to be for 75–90% in the ADP-sensitive E₁-conformation.     

Stereoselective metabolism of 7-methylbenz[a]anthracene: absolute configuration of five dihydrodiol metabolites and the effect of dihydrodiol conformation on circular dichroism spectra

7-Methylbenz[a]anthracene (7-MBA) was metabolized stereoselectively by rat liver microsomes to form five optically active dihydrodiols as the predominant metabolites. The dihydrodiols were purified by a combination of reversed-phase and normal-phase high performance liquid chromatography (HPLC). By comparison of their circular dichroism (CD) spectra with the corresponding benz[a]anthracene (BA) dihydrodiols of known absolute stereochemistry, the major dihydrodiol enantiomers of 7-MBA have been determined to have 1R,2R-, 3R,4R- and 10R , 11R - absolute configurations, respectively. Due to their quasi- diaxial conformations, the absolute configuration of trans-5,6- and trans-8,9-dihydrodiols, the two most abundant metabolites of 7-MBA, could not be determined by simple comparisons of their circular dichroism spectra with those of the quasidi -equatorial BA 5R, 6R - and 8R , 9R -dihydrodiols. The major enantiomers of the quasi- diaxial trans-5,6- and trans-8,9-dihydrodiol metabolites of 7-MBA were determined by comparison to the CD spectrum of 7-bromo-BA 5R, 6R -dihydrodiol and by the exciton chirality method to have R,R absolute stereochemistry. This study also revealed that the circular dichroism Cotton effects of an enantiomeric dihydrodiol of polycyclic aromatic hydrocarbons can be drastically altered if the conformation (quasi- diaxial vs. quasi di-equatorial ) of the dihydrodiol is changed.     

Marijuana exposure in vivo and human lymphocyte chromosomes.

Sequential chromosome examinations of peripheral lymphocte cultures were carried out on 21 adult male volunteers who smoked natural blend marijuana cigarettes containing about 1%, 2%, or no delta9-THC. For a limited number of subjects, blood samples from a single venipuncture were cultured independently in two cytogenetic laboratories, and later the slides were exchaged for re-analysis. There were significant differences between laboratories in the absolute break frequencies recorded. These inter-laboratory differences were demonstrated for both techniques of cell culture and metaphase analysis. Neither laboratory found a statistically significant increase in break frequencies asssociated with marijuana smoking. The present study, therefore, failed to detect a measurable effect of marijuana smoking on chromosomal aberrations in subjects experienced in the use of the drug.