Infectivity,viability and effects of Paranosema locustae (Microsporidia) on juveniles of Dichroplus maculipennis (Orthoptera: Acrididae: Melanoplinae) under laboratory conditions

Infectivity and effects on host of a long-term stored aqueous suspension of Paranosema locustae on juveniles of Dichroplus maculipennis, a pest grasshopper in parts of the Pampas and Patagonia, were evaluated. Infections developed in 90–97.8% of treated individuals. Mortality increased with time, reaching highest values at 30–40 days post-inoculation (79.5–100%). Infected nymphs showed significantly slower development.     

Transformation of Nicotiana tabacum,N. debneyi,and N. rustica: Inheritance and protoplast expression of antibiotic resistance

Agrobacterium tumefaciens strains harbouring plasmid vectors pBCAT1, pVU1011 or pMON806 were used to transform leaf explants of Nicotiana tabacum cultivars Delgold and Candel, N. debneyi, and N. rustica var. NRT. Transgenic plants resistant to the selective agents kanamycin, hygromycin or methotrexate were regenerated and used as sources of leaf mesophyll protoplasts. Protoplasts divided and regenerated plants in the presence of selective agents at levels inhibitory to protoplasts of non-transformed plants. Cross-resistance of protoplasts to more than one selective agent was not observed in this study which suggests that this approach may lead to an efficient interspecific somatic hybrid selection system.     

Deactivation of the Photosystem II oxidation (S) states by 2-(3-chloro-4-trifluoromethyl)anilino-3,5-dinitrothiophene (ANT2p) and the putative role of carotenoid

Addition of 2-(3-chloro-4-trifluoromethyl)anilino-3,5-dinitrothiophene (ANT2p) to detergent-solubilised Photosystem II (PS II) particles results in the photo-oxidation of carotenoid and inhibition of the steady-state oxygen-evolution rate. It has been proposed that ANT2p may modify the water-splitting reactions by mediating the transfer of reducing equivalents from endogenous electron donors, such as carotenoid, to the S₂ and S₃ oxidation states of PS II. In this paper we present evidence indicating that ANT2p can interact with PS II at two separate loci. The water-splitting complex is shown to be the primary site of attack by ANT2p, since artificial electron donors, such as 1,5-diphenylcarbazide (DPC), can restore PS II photochemical activity by feeding reducing equivalents directly to the reaction centre. The ANT2p interaction at this site is light-intensity dependent. A second inhibitory site close to the reaction centre P-680 chlorophyll is detected at slightly higher ANT2p concentrations. The inhibition at this site is unaffected either by changes in the actinic light intensity or by the addition of electron donors. The flash-induced oxidation of carotenoid has an ANT2p concentration dependence and an insensitivity to DPC which suggests that it results from the inhibition of the reaction centre and not with that of the water-splitting complex.     

Effects of piretanide on plasma fibrinolytic activity,platelet aggregation and platelet factor-4 release in man

Piretanide, 4-phenoxy-3-(pyrrolidinyl)-5-sulphamoyl benzoic acid, apart from being an efficient diuretic, enhances endogenous plasma fibrinolytic activity after a single dose of 6 mg administered by oral route. After ingestion of the drug, acceleration of fibrinolytic acitivity became manifest within 1 h, reached its peak in 3 h and was associated with a fall in fibrinogen and diminished urokinase excretion. Piretanide did not cause lysis of fibrinin vitro. Primary platelet aggregation, induced by adenosine-diphosphate, was inhibited by piretanide. Inin vitro experiments piretanide led to effective inhibition of adenosine-diphosphate-induced platelet aggregation with complete inhibition at 5 mM concentration. Piretanide led to a highly significant decrease of platelet factor-4 release.     

Redox conditions for stimulation of in vitro folding and assembly of the glycoprotein hormone chorionic gonadotropin

The formation of native disulfide bonds during in vitro protein folding can be limiting in obtaining biologically active proteins. Thus, optimization of redox conditions can be critical in maximizing the yield of renatured, recombinant proteins. We have employed a folding model, that of the beta subunit of human chorionic gonadotropin (hCG- beta), to investigate in vitro oxidation conditions that facilitate the folding of this protein, and have compared the in vitro rates obtained with the rate of folding that has been observed in intact cells. Two steps in the folding pathway of hCG-beta were investigated: the rate-limiting events in the folding of this protein, and the assembly of hCG-beta with, hCG-alpha. The rates of these folding events were determined with and without protein disulfide isomerase (PDI) using two different types of redox reagents: cysteamine and its oxidized equivalent, cystamine, and reduced and oxidized glutathione. Rates of the rate-limiting folding events were twofold faster in cysteamine/cystamine redox buffers than in glutathione buffers in the absence of PDI. Optimal conditions for hCG-beta folding were attained in a 2 mM glutathione buffer, pH 7.4, that contained 1 mg/mL PDI and in 10muM cysteamine/cystamine, pH 8.7, without PDI. Under these conditions, the half-time of the ratelimiting folding event was 16 to 20 min and approached the rate observed in intact cells (4 to 5 min). Moreover, folding of the beta subunit under these conditions yields a functional protein, based on its ability to assemble with the alpha subunit. The rates of assembly of hCG-beta with hCG-alpha in the cysteamine/cystamine or glutathione/PDI redox buffers were comparable (t(1/2/sb> = 9 to 12 min)). These studies show that rates of folding and assembly events that involve disulfide bond formation can be optimized by a simple buffer system composed of cysteamine and cystamine. (c) 1994 John Wiley & Sons, Inc.     

Piper longum Constituents Induce PANC-1 Human Pancreatic Cancer Cell Death under Nutrition Starvation

Pancreatic cancer is a highly aggressive form of cancer with a poor prognosis, partly due to ‘austerity’, a phenomenon of tolerance to nutrient deprivation and survival in its hypovascular tumor microenvironment. Anti-austerity agents which preferentially diminish the survival of cancer cells under nutrition starvation is regarded as new generation anti-cancer agents. This study investigated the potential of Piper longum constituents as anti-austerity agents. The ethanolic extract of Piper longum was found to have preferential cytotoxicity towards PANC-1 human pancreatic cancer cells in a nutrient-deprived medium (NDM). Further investigation led to the identification of pipernonaline ( 3 ) as the lead compound with the strongest anti-austerity activity, inducing cell death and inhibiting migration in a normal nutrient medium, as well as strongly inhibiting the Akt/mTOR/autophagy pathway. Therefore, pipernonaline ( 3 ) holds promise as a novel antiausterity agent for the treatment of pancreatic cancer.     

多金属矿中微量BeO的测定

试验在ｐＨ１０．０～１１．０条件下,用络天青Ｓ（ＣＡＳ）和溴化十六烷基吡啶（ＣＰＢ）、Ｔｒｉｔｏｎｘ—１００与铍形成橙色四元络合物,其最大吸收波长为５０８ｎｍ,采用酒石酸、柠檬酸钠、ＥＤＴＡ、三乙醇胺等作为掩蔽剂,可消除多种共存离子的干扰直接测定多金属矿中微量氧化铍,本法灵敏度高（ε＝３．７５×１０４）,稳定性及重现性较好,ＢｅＯ含量在０～８μｇ／５０ｍｌ符合比尔定律。     

Towards MRI contrast agents of improved efficacy. NMR relaxometric investigations of the binding interaction to HSA of a novel heptadentate macrocyclic triphosphonate Gd(III)-complex

 A novel heptacoordinating ligand consisting of a thirteen-membered tetraazamacrocycle containing the pyridine ring and bearing three methylenephosphonate groups (PCTP-[13]) has been synthesized. Its Gd(III) complex displays a remarkably high longitudinal water proton relaxivity (7.7 mM^–1 s^–1 at 25  °C, 20 MHz and pH 7.5) which has been accounted for in terms of contributions arising from (1) one water molecule bound to the metal ion, (2) hydrogen-bonded water molecules in the second coordination sphere, or (3) water molecules diffusing near the paramagnetic chelate. Variable-temperature ¹⁷O-NMR transverse relaxation data indicate that the residence lifetime of the metal-bound water molecule is very short (8.0 ns at 25  °C) with respect to the Gd(III) complexes currently considered as contrast agents for magnetic resonance imaging. Furthermore, GdPCTP-[13] interacts with human serum albumin (HSA), likely through electrostatic forces. By comparing water proton relaxivity data for the GdPCTP-[13]-HSA adduct, measured as a function of temperature and magnetic field strength, with those for the analogous adduct with GdDOTP (a twelve-membered tetraaza macrocyclic tetramethylenephosphonate complex lacking a metal-bound water molecule), it has been possible to propose a general picture accounting for the main determinants of the relaxation enhancement observed when a paramagnetic Gd(III) complex is bound to HSA. Basically, the relaxation enhancement in these systems arises from (1) water molecules in the hydration shell of the macromolecule and protein exchangeable protons which lie close to the interaction site of the paramagnetic complex and (2) the metal bound water molecule(s). As far as the latter contribution is concerned, the interaction with the protein causes an elongation of the residence lifetime of the metal-bound water molecule, which limits, to some extent, the potential relaxivity enhancement expected upon the binding of the paramagnetic complex to HSA. Received: 27 January 1997 / Accepted: 12 May 1997     

DNA topoisomerase activities in concanavalin A-stimulated lymphocytes

Topoisomerase activities have been measured in nuclear extracts of concanavalin A-stimulated lymphocytes. In parallel with the wave of DNA synthesis, type II topoisomerase activity was considerably increased. After 72 h treatment, this activity was stimulated approx. 20-fold over the activity in untreated cells. In contrast, type I topoisomerase was poorly stimulated after 24 h treatment, and 4-5-fold after 72 h. These findings, together with our previous results on regenerating rat liver, suggest a major role of topoisomerase II in DNA replication.     

Modulation of platelet responsiveness through selective phosphorylation of plasma membrane proteins: Antagonistic eeffects of cyclic AMP and cyclic GMP

³²P phosphorylation of plasma membranes from human blood platelets, under conditions that closely resemble physiological ones (endogeneous phosphate donors and intact platelets in homologous plasma), result in the incorporation of the label mainly in a membrane glycoprotein of apparently high molecular weight (greater than 400 000). Dibutyryl cyclic AMP, an inhibitor of platelet aggregation, specifically increases the degree of phosphorylation of this glycoprotein. Moreover, it has been found that prostaglandin E₁ one of the most potent inhibitors of platelet aggregation which also increases phosphorylation of the same glycoprotein, is significantly more effective than cyclic AMP.Cyclic GMP does not have any apparent effect on platelet aggregation. However, incubation of platelet-rich plasma with both cyclic GMP and cyclic AMP results in a partial recovery of the platelet responsiveness towards ADP-induced aggregation. Coincidently, the degree of phosphorylation of the high molecular weight glycoprotein under these conditions, although still higher than in controls (no nucleotides added), is significantly decreased as compared with cyclic AMP-treated cells. Furthermore, cyclic GMP inhibits the cyclic AMP-dependent protein kinase activity in isolated platelet plasma membranes.These results suggest a central role for this membrane phosphoglycoprotein in the triggering of platelet aggregation and, furthermore, suggest that modulation of its degree of phosphorylation may be exerted through some cyclic AMP/cyclic GMP relationship, which in the basal state might be critical for platelet responsiveness.