双胸蚓纤溶酶的纯化及性质

 用硫酸铵分段盐析、超滤膜分级分离及DEAE-纤维素、Sephadex A-25和Sephadex G-50三种柱层析方法从双胸蚓组织的粗提取液中分离纯化出一种纤溶酶,分子量为29kD,由一条肽链组成。此晦具有强烈的溶解纤维蛋白的作用,对家兎实验性血凝块也具有明显的溶解作用。此酶的最适pH为8.0,在pH7.6～8.4之间活力相差不到2％;酶在PH4.7—11.0范围内稳定;酶作用的最适温度为57℃;此酶热稳定性较好,于25～50℃保温3小时,酶活力基本不变,60℃时,活力保留65％。金属离子Na~(+)、K~(+)、Mg~(2+)等可提高此酶的活力,而Hg~(2+)、Ca~(2+)等金属离子对此酶有不同程度的抑制作用。     

El Tor型霍乱弧菌及其细胞壁缺陷型分子遗传学背景的研究

El Tor 型霍乱弧菌(以下简称 El Tor 弧菌)可以在人工培养条件下长期存活。当微环境改变时可形成细胞壁有不同程度缺陷的菌株如抗噬菌体突变株或 L 型菌株。我们以 DNA 酶切图谱和 El Tor 弧菌溶血素、神经氨酸酶基因探针杂交图谱为参数对 El Tor 弧菌的野生型及其细胞壁缺陷型变异株在遗传背景上进行了比较分析研究。结果提示细胞壁缺陷型菌株与其野生型在DNA 水平上高度同源。此外,文中还介绍了一种从 L 型菌株中制备 DNA 的方法。     

Catalysis by Laccase (From Coriolus uersicolor) in Microheterogeneous Media of the Water/Organic Solvent/Surfactant Type

Catalysis by laccase from Coriolus uersicolor solubilized in the ternary systems of surfactant/water/organic solvent type, namely, Aerosol OT/water/octane, Brij 56/water/cyclohexane and egg lecithin/water/octane + pentanol + methanol mixture, has been studied. The laccase activity is found to depend, in principle, not only on the water/surfactant molar ratio, but on the surfactant concentration (with its hydration degree being constant) as well. The following inferences should be emphasized. Firstly, in all the systems under study, the catalytic activity (k_cat) of laccase entrapped into surfactant reversed micelles increases more than 50 times (when the surfactant concentration is extrapolated to zero) compared with the k_cat value in aqueous solution. Secondly, the catalytic activity (k_cat) of laccase entrapped in hydrated Aerosol OT aggregates, having lamellar, reversed cylindrical (hexagonal) and reversed micellar structure, depends greatly on the aggregate type. In other words, the phase transitions, i.e. an alteration in the packing of hydrated Aerosol OT molecules, evokes a sharp reversible change in the enzymatic activity. Thirdly, in the same phase, the catalytic activity of the solubilized enzyme depends on the linear dimensions of water cavities inside the surfactant aggregates (i.e. on the water content in the system under study). All these effects, regulating enzymatic activity, are probably caused by an alteration of the conformational mobility of laccase molecules incorporated into the inner polar cavities inside the surfactant aggregates.     

Penetration of intact bovine ova with ram sperm in vitro

In culture, mature bovine ovarian oocytes were fertilized in vitro with freshly ejaculated ram spermatozoa treated with heparin. The zona pellucida does not prevent penetration of ram spermatozoa. The penetration rate varied between 10 and 84%, and in most instances, after 24 hr of culture, two normal-looking pronuclei and sperm tail were present in the cytoplasm. These results suggest that the zona pellucida of bovine oocytes does not represent a barrier for the penetration of ram spermatozoa.     

Subjective experiences associated with thermal biofeedback treatment of hypertension

Reports of subjective experiences of 73 hypertensive patients who were treated with thermal biofeedback for hand warming were obtained over 16 treatment sessions. Most of the differential responding in subjective report occurred in the first 5 sessions. Differences in reports of throbbing were associated with medication status during treatment (presence of sympatholytic antihypertensive agent). From 4 to 9% of patients report negative subjective experiences at any one session. When short-term clinical successes (either elimination of medication or reduction of BP) were compared with short-term failures, it was found that successes reported more warmth, more likelihood of falling asleep, and more dreamlike experiences. The latter were more likely to occur suddenly for the successes. Correlational analyses revealed consistent positive associations between reports of warmth and relaxation with highest temperature achieved in the session and consistent negative associations between experiencing physical sensations and degree of temperature change within the session.This research was supported in part by grants from NHLBI, HL-27622 and HL-31189.     

Redox Properties Of Phenols, Their Relationships To Singlet Oxygen Quenching And To Their Inhibitory Effects On Benzo(A)Pyrene-Induced Neoplasia

The inhibitory effects of synthetic phenolic compounds on benzo(a)pyrene-induced neoplasia of the mouse forestomach have been measured by Wattenberg et al⁶ The efficiency of this inhibition has been estimated for each phenol, using R, the ratio of the number of tumors per mouse in the protected group over the number of tumours per mouse in the control group. We have observed a linear correlation between the chemoprotection efficiency R and the logarithm of the rate of quenching of singlet oxygen. k. by this family of phenols, log k being itself correlated with the one-electron oxidation potential of the phenols. These correlations suggest a charge transfer mechanism for the inhibition of neoplasia induced hy benzo(a)py-rene. The correlations described provide a theoretical basis for scaling the inhibitors of mutagenicity induced by polycyclic aromatic compounds in terms of their oxidation potentials     

Radical Cations in Aromatic Hydrocarbon Carcinogenesis

Most carcinogens, including polycyclic aromatic hydrocarbons (PAH), require metabolic activation to produce the ultimate electrophilic species that bind covalently with cellular macromolecules to trigger the cancer process. Metabolic activation of PAH can be understood in terms of two main pathways: one-electron oxidation to yield reactive intermediate radical cations and monooxygenation to produce bay-region diol epoxides. The reason we have postulated that one-electron oxidation plays an important role in the activation of PAH derives from certain common characteristics of the radical cation chemistry of the most potent carcinogenic PAH. Two main features common to these PAH are: 1) a relatively low ionization potential, which allows easy metabolic removal of one electron, and 2) charge localization in the PAH radical cation that renders this intermediate specifically and efficiently reactive toward nucleophiles. Equally important, cytochrome P-450 and mammalian peroxidases catalyze one-electron oxidation. This mechanism plays a role in the binding of PAH to DNA. Chemical, biochemical and biological evidence will be presented supporting the important role of one-electron oxidation in the activation of PAH leading to initiation of cancer.     

Two-compartment model for rabbit skin organ culture

Summary A new method was developed for rabbit skin organ culture. In a two-compartment model, skin discs were cultured on a Millicell-HA insert unit with a microporous membrane which allows transport of culture medium via the dermis into the epidermis, whereas the epidermal side remains free of direct contact with culture medium. In this relatively simple two-compartment organ culture model, rabbit skin could be cultured for 7 d in RPMI 1640 medium supplemented with fetal bovine serum, or for 2 d in RPMI 1640 medium supplemented with cofactors. The histomorphology and ultrastructure of 7-d cultured rabbit skin discs was essentially similar to that of freshly isolated rabbit skin. Keratinocytes in the stratum basale continued to divide during organ culture. The terminal differentiation of the epidermis continued in vitro as was found by the presence of keratohyalin granules, the intact stratum corneum, and keratin expression. Furthermore, glucose consumption continued until culture Day 7, but thereafter it declined rapidly. Concomitantly, degenerative changes were found. At the end of the 7-d culture period the distance between single dermal collagen fibrils had increased as compared to noncultured skin. This model of skin organ cultures can be used to study biological processes, dermal toxicity, and penetration and metabolism of xenobiotics in intact skin. Furthermore, within certain limits, processes responsible for repair and regeneration of damaged skin can also be studied in this model because the rabbit skin can be cultured for 7 d. The present study was financially supported by grants of Duphar B. V. (Weesp, Netherlands), the European Community, and the Dutch animal welfare organizations Samenwerkingsverband van de Nederlandse Vereniging tot Bescherming van Dieren en de Nederlandse Bond tot Bestrijding van de Vivisectie, Anti-Vivisectie Stichting en Stichting Schoonheid Zonder Wreedheid.     

Evaluation ofHadena perplexa [Lepidoptera: Phalaenidae] as a biocontrol agent of bladder campionSilene vulgaris [Caryophyllaceae] in Canada: Rearing and host specificity

Rearing techniques and results of preliminary host range tests are reported forHadena perplexa (Denis & Schiffermuller) (Lep.: Phalaenidae) a candidate biocontrol agent against the weed bladder campion,Silene vulgaris (Moench) Garcke, in Manitoba, Canada. In the laboratory, it was necessary to pipette a 15% honey solution in water into the flowers as food for the adult moths. When reared singly to avoid cannibalism, 56% of the 1^st instar larvae developed to pupae. Larvae fed on a natural diet for 10 days can then be reared on either one of 2 artificial diets. Choice oviposition tests and no-choice larval feeding tests were conducted with plant species closely related toS. vulgaris in the generaSilene, Dianthus, Gypsophila, Lychnis, Saponaria. Species in 4 of 5 of these genera were accepted for oviposition, and species in all 5 genera supported the development of 1^st instar larvae to the pupal stage.H. perplexa should not be introduced into Canada.      

Canopy structures and its effect on shoot growth and flowering in subalpine forests

Changes in foliage density distribution with altitude and its effect on shoot growth and flowering were studied in forest section planes (profiles) of subalpine forests and scrubs (Krummholz) in Nepal and Japan.Patterns of foliage in forest canopy were evaluated by an analysis of variance. Foliage densities were very high at high altitude canopies, but the change in spatial patterns along altitude differs in both areas.The spatial pattern of new shoot production was similar to that of current foliage density and was affected by the amount of foliage above the sample probably through light condition. Flowering of tall trees occurred in the surface of the upper canopy, but a shrub species flowered even under tree canopies.