Studies on the induction and expression of T-cell-mediated immunity. XIII. Membrane-associated antigens of cytotoxic T lymphocytes involved in cytotoxicity

An xenogeneic rat anti-mouse T-cell serum, designated RAT*, has been shown to block the cytolytic activity of cytotoxic T lymphocytes (CTL) at a postbinding step. RAT* serum or the IgG fraction was extensively absorbed with the target cell, P815, a DBA mastocytoma, and used with or without further absorption to immunoprecipitate specific molecules from radiolabeled membrane extracts of CTL derived from either in vivo-allosensitized mice or from cytotoxic clones maintained in in vitro cultures. Cell surface sialic acid residues were labeled by oxidation with sodium periodate (NaIO4) and reduction with tritiated sodium borohydride ([3H]NaBH4). Alternatively, cell surface proteins were labeled with 125I by lactoperoxidase-catalyzed iodination. Nonidet P-40 (NP-40)-solubilized radiolabeled membranes were then immunoprecipitated with RAT* serum and analyzed by sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis (PAGE). Three membrane-associated molecules of 95,000, 140,000 and 180,000 Mr were found by such analysis. The sensitivity of these three molecules to trypsinization and their susceptibility to labeling with [3H]NaBH4 suggested that they are glycoproteins. Moreover, when RAT* serum or the IgG fraction was absorbed with various cell types, its ability to immunoprecipitate the three molecules correlated with its ability to block cytolysis. Adsorption of RAT* serum with CTL, but not with nonimmune thymocytes, significantly reduced the ability of RAT* serum to inhibit cytotoxicity and to immunoprecipitate the 95k, 140k, and 180k molecules. Thus, these findings suggest that one or more of these cell surface molecules of CTL may be involved in the cytolytic process.     

Highly purified particulate guanylate cyclase from rat lung: characterization and comparison with soluble guanylate cyclase

Guanylate cyclase was purified 1000-fold from washed rat lung particulate fractions to a final specific activity of 500 nmoles cyclic GMP produced/min/mg protein by a combination of detergent extraction and chromatography on concanavalin A-Sepharose, GTP-agarose, and blue agarose. Particulate guanylate cyclase has a molecular weight of 200 000 daltons, a Stokes radius of 48 A and a sedimentation coefficient of 9.4 while the soluble form has a molecular weight of 150 000 daltons, a Stokes radius of 44 A, and a sedimentation coefficient of 7.0. Whereas the particulate enzyme is a glycoprotein with a specific affinity for concanavalin A and wheat germ agglutinin, the soluble form of guanylate cyclase did not bind to these lectins. Purified particulate guanylate cyclase did not cross-react with a number of monoclonal antibodies generated to the soluble enzyme. While both forms of the enzyme could be regulated by the formation of mixed disulfides, the particulate enzyme was relatively insensitive to inhibition by cystine. With GTP as substrate both forms of the enzyme demonstrated typical kinetics, and with GTP analogues negative cooperativity was observed with both enzyme forms. These data support the suggestion that the two forms of guanylate cyclase possess similar catalytic sites, although their remaining structure is divergent, resulting in differences in subcellular distribution, physical characteristics, and antigenicity.     

Adaptive Functions of Vertebrate Molting Cycles

SYNOPSIS Cyclic epidermal cellular prohfeiation,with or withoutkeratinization is a vertebrate characteristic Such activityprobably obeys an autonomous rhythm which is legulated throughneuro humoral S)stcms in response to envnonmental (piox imate)stimuliand related to adaptive (ultimate) factors In seeking causeand effect lelationships, however, it becomes apparent thatthe same environmental parameter may be both an ultimate anda pioximate factor, the latter also regulating the rate of lesponseWith regard to molting in homoio'heims, tempeiatuie acts insuch a capacity in many species Peiiodic shedding of the outer epidermis in fish amphibiansand reptiles does not appear to be coirelated with seasonalfactors to the extent that avian and mammalian molts are The evolution of vertebrate molting cycles has amounted to theentraining of inherent epidermal C)cles with seasonal demandsby the organism itself and the environment,these demands actas regulating mechanisms Pieadapted structures such as feathersand hairs function collectively as plumage and pelage in theirvarious roles but separately in their growth and leplacementcycles which, however, are coordinated for maximum functionalefficiency Molting is also synchionized with the seasonal cycleaccording to the availability of energy resources and time tocomplete the essential functions (in addition to molting) Theevolved molting systems as manifested in the gieat variety ofpatterns and types in the vertebrates, may thus be legardedas almost individual responses to selective piessures actingon a umveisil vertebrate chaiacter The basic regulatoiy system involves the neuro hvpophyseal complexwhich contiols target endocrines affecting various functionswhich themselves influence epidermal mitosis and, ultimately,molting 1 he mechanism in its simplest form controls the animalsmetabolism through the thyroid acting independently in a permissivecapacity or synergistically with the adrenal and gonadal hormoneswhich are regulated directly and/or indirectly through negativefeedback     

Quantum theory of nerve excitation

Based on quantum transitions of membrane dipoles, the four fundamental properties of nerve impulse are derived in this paper: the all-or-none response, the strength-duration relation, refractoriness and refractory period and frequency modulation. Furthermore, the theory offers a physical mechanism for nerve excitation similar to a two-level ammonia maser. It also implies non-threshold excitation at elevated temperatures. The role of trimethylamine ions near the surface of a phospholipid membrane is briefly discussed to indicate a possible connection between theory and reality.     

Nucleoside Diphosphate-sugar 4-Epimerases I. Uridine Diphosphate Glucose 4-Epimerase of Wheat Germ

Uridine diphosphate (UDP)-glucose 4-epimerase (EC 5.1.3.2) has been purified over 1000-fold from extracts of wheat germ by MnCl₂ treatment, (NH₄)₂SO₄ fractionation, Sephadex column chromatography, and adsorption onto and elution from calcium phosphate gel. The enzyme has a pH optimum of 9.0. Km values are 0.1 mm for UDP-d-galactose and 0.2 mm for UDP-d-glucose. NAD is required for activity; K_a = 0.04 mm. NADH is an inhibitor strictly competitive with NAD; K_i = 2 μm. Wheat germ also contains UDP-l-arabinose 4-epimerase (EC 5.1.3.5) and thymidine diphosphate (TDP)-glucose 4-epimerase which are distinct from UDP-glucose 4-epimerase.     

胎盘型碱性磷酸酶的纯化及部分性质的研究

 <正> 胎盘型碱性磷酸酶(P-ALP)是碱性磷酸酶(EC3.1.3.1.ALP)的一种同工酶。P-ALP除出现于妊娠妇女血清外,一些学者还从恶性肿瘤患者血清中发现此酶,并证明它是一种特异性较强的肿瘤标志物。据此,建立P-ALP的简易纯化方法,制备纯度较高的酶制品是建立P-ALP灵敏的微量检测法的先决条件。本文报道以L-苯丙氨酸(L-phe)为配基,用氯代环氧丙烷活化Sepharose 4B的亲和层析法,从人胎盘纯化P-ALP,并对其部分性质进行了研究。     

Principles and applications of luminescence spectrometry coupled to liquid chromatographic techniques

An overview is presented of the physicochemical basis of luminescence, and its application to the detection of chemicals (drugs, biomedically important compounds, environmentally active substances) in liquid chromatographic systems.     

胡萝卜人工种子在无菌条件下的贮藏及贮藏中种子活力变化

对用海藻酸钙包埋胡萝卜体细胞胚(0.6—2mm)制作的人工种子进行贮藏研究,发现低温及干燥均能在一定程度上抑制人工种子萌发。失水率达67%的种子,2℃贮藏60天后, 在发芽培养基上发芽率为100%,7天内的成苗率达80%。未经贮藏的对照种子发芽率为100%,成苗率为76%。无论在“种皮”还是在胚胎悬浮培养液中加入脱落酸或香豆素,都能抑制胚的生长,但也促进了胚的衰老。铝箔袋内密闭贮藏期间种子不萌发,但活力下降快。随着贮藏时间的延长,种子的活力指数、脱氢酶活性、氧吸收率都呈下降趋势。