Isolation of Two Plasticizers,Bis(2-ethylhexyl) Terephthalate and Bis(2-ethylhexyl) Phthalate,from Capparis spinosa L. Leaves

Many plants have been known to be contaminated and accumulate plasticizers from the environment, including water sources, soil, and atmosphere. Plasticizers are used to confer elasticity and flexibility to various fiber and plastic products. Consumption of plasticizers can lead to many adverse effects on human health, including reproductive and developmental toxicity, endocrine disruption, and cancer. Herein, we report for the first time that two plasticizers, bis(2-ethylhexyl) terephthalate (DEHT) and bis(2-ethylhexyl) phthalate (DEHP), have been isolated from the leaves of Capparis spinosa L. (the caper bush), a plant that is widely used in food seasonings and traditional medicine. 297 mg/kg of DEHT and 48 mg/kg of DEHP were isolated from dried and grounded C. spinosa L. leaves using column chromatography and semi-preparative high-performance liquid chromatography. Our study adds to the increase in the detection of plasticizers in our food and medicinal plants and to the alarming concern about their potential adverse effects on human health.     

Ion binding constants for gramicidin a obtained from water permeability measurements

Gramicidin A pores are permeable to water and small monovalent cations. For K, Rb, and Cs there is good evidence from conductances and permeability ratios that a second ion can enter a pore already occupied by another, but for Na this evidence is inconclusive and comparison of tracer fluxes and single channel conductances suggests that second ion entries are prohibited. Partly as a result of the complications of second ion entry there have been widely differing estimates for the dissociation constants for the first ion in the channel. Dani and Levitt (1981, Biophys. J. 35: 485–499) introduced a method for calculating ion binding constants from simultaneous measurements of water fluxes and membrane conductance. They found no evidence for second ion binding and calculated dissociation constants of 115 mm for Li, 69 mm for K, and 2 mm for Tl. It is shown here that the two-ion, four-state model predicts a dependence of water permeability on ion concentration that is difficult to distinguish from the predictions of block by a single ion. Using a modified technique that allows measurement of higher conductances, the first ion dissociation constants have been determined as 80 mm for Na, 40 mm for Rb and 15 mm for Cs. These values and those of Dani and Levitt fall in a smooth sequence. The dissociation constant for Cs is consistent with single channel conductances and flux ratios. There is a discrepancy between this constant for Na and the value, 370 mm, calculated from the single channel conductances and the assumption that a second ion cannot enter or affect an occupied pore. The dissociation constant for Rb is intermediate between those for K and Cs whereas tracer flux measurements (Schagina, Grinfeldt & Lev, 1983. J. Membrane Biol. 73: 203–216) have suggested that Rb interacts much more strongly with the channel than Cs.We should like to thank the National Grid plc, for the grant which supported K.-W.W., the Wellcome Trust for a visiting Fellowship for S.T. in Cambridge, and the Cambridge Society of Bombay which supported S.B.H. in Bombay.     

Prothrombin cleavage by human vascular smooth muscle cells: A potential alternative pathway to the coagulation cascade

Thrombin is a potent mitogen for human vascular smooth muscle cells (HVSMC) and its enzymatic activity is required for this function. The present study demonstrates that prothrombin is also mitogenic for HVSMC due to the generation of enzymatically active thrombin which occurs upon incubation of prothrombin with the cells. Analysis by SDS-PAGE, immunoblotting, and amino acid sequencing revealed that prothrombin incubated with HVSMC undergoes limited proteolysis. Prethrombin 1 was formed through cleavage at R¹⁵⁵-S¹⁵⁶. Cleavage at R²⁷¹-T²⁷² generated fragment 1.2 and prethrombin 2 whilst cleavage at R²⁸⁴-T²⁸⁵ yielded truncated prothrombin 2 (prethrombin 2′). However, cleavage at R³²⁰-I³²¹ which, during prothrombin activation produces two-chain α-thrombin, was not detectable. Studies on HVSMC-conditioned medium revealed that a similar pattern of prothrombin cleavage occurred by a cell-secreted factor(s). Amidolytic activity analysis indicated that 1–3% catalytically active thrombin-like activity was generated upon incubation of prothrombin with HVSMC-conditioned medium. By treating conditioned medium with various classes of proteinase inhibitors or hirudin, it was determined that prothrombin is cleaved by a cell-derived serine proteinase-like factor(s) at R²⁷¹-S²⁷² and by α-thrombin at R¹⁵⁵-S¹⁵⁶ and R²⁸⁴-T²⁸⁵. Antibodies neutralising the activity of either urokinase, tissue plasminogen activator, or factor Xa failed to alter the prothrombin cleaving activity of conditioned medium. This activity which may catalyse an alternative pathway for the generation of thrombin, was eluted from a gel filtration column as a single peak with apparent molecular mass of 30–40 kDa. © 1995 Wiley-Liss, Inc.     

Effect of temperature and baroreceptor stimulation on reflex venomotor responses

To investigate the interaction of thermal reflexes and baroreflexes in the control of the peripheral veins, we studied in supine humans the effects of lower body negative pressure (LBNP) and neck suction (NS) on forearm veins at ambient temperatures (Ta) of 18, 28, and 37 degrees C. Forearm venous volume (FVV)-venous pressure (FVP) relations (forearm venous capacitance) on six subjects showed an increase from 18 through 28 to 37 degrees C (P less than 0.001). Heart rate increased (P less than 0.001) and forearm venous capacitance decreased (P less than 0.001) in proportion to the level of LBNP applied from 20 to 50 Torr at all Ta. At 50 Torr LBNP, FVV at 30 cmH2O, FVP decreased from control values of 2.5, 3.8, and 4.4 to 1.6, 2.7, and 3.4 ml/100 ml at 18, 28, and 37 degrees C, respectively. We also studied venomotor responses using the occluded limb technique. Although LBNP caused venoconstriction, NS applied either alone or during LBNP produced no change in venomotor tone. Therefore we concluded that carotid baroreceptors play little role in reflex venomotor adjustments. Since changes in mean arterial and pulse pressures during LBNP did not account for the observed venomotor responses, we concluded that low-pressure baroreceptors initiate significant venoconstrictor reflexes over a wide range of Ta.     

Allelopathic effects ofEupatorium riparium on population regulation of two species ofGalinsoga and soil microbes

Summary Allelopathic effect ofEupatorium riparium Regel, a dominant ruderal weed at higher altitudes in Meghalaya state in north-eastern India, was studied on two common sympatric annual weeds,Galinsoga ciliata (Raf.) andG. parviflora Cav. and on soil microbes. Seed germination and radicle and plumule growth of both species ofGalinsoga were suppressed by the aqueous extract and leachate ofE. riparium. Although the leaf leachate, leaf and litter extracts and litter bed caused considerable reduction in leaf area and seed and dry matter production in both species ofGalinsoga, the effect was much more pronounced onG. parviflora. The inhibitory effect was directly correlated with the concentration of the extract and leachate. The soil microbial population and growth of theGalinsoga spp. declined considerably in the experimental pots where the soil had earlier received leachate of different plant parts ofE. riparium growing in it. The presence of the partly decomposed litter ofE. riparium in the pots reduced soil microbial population and growth of the two weeds much more strongly as compared to the litter in the advanced stages of decomposition. The study also revealed that the abundance and colony growth of the two test fungiviz. Trichoderma viride andAspergillus flavus were differentially affected by the allelopathy ofE. riparium; T. viride being favoured andA. flavus inhibited.     

Characterization and Translation of Poly(A)+RNA from Wounded and Crown Gall Tissues of Potato Tubers

Poly(A)⁺ and poly(A)^–RNA from wounded potato tuber tissuesand crown gall tumors were separated from total RNA by oligodeoxythymidylicacid-cellulose affinity chromatography. The poly(A)⁺RNA wascharacterized by sucrose density gradient centrifugation, hybridizationwith ³(H)polyuridylic acid [Poly(U)] and in vitro translationin a rabbit reticulocyte lysate system. The tumor poly(A)⁺RNAwas a heterodisperse mixture from 3.5S to 35S. Upon poly(U)hybridization of the gradient fractions two major hybridizationpeaks at 7S and 21S and two peaks at 11S and 16S appeared. Inan in vitro translation system the poly(A)⁺RNA programmed thesynthesis of 23 different polypeptides of 9,000 to 79,800 daltonsmolecular weight as determined by SDS-polyacrylamide gel electrophoresis.The 21S poly(A)+RNA was about 5 times more active in in vitroprotein synthesis than the 7S poly(A)⁺RNA. The poly(A)⁺RNA from wounded tissues was also heterodisperse(from 4.5S to 31S) with a modal peak at 18S. This RNA codedfor at least 28 polypeptides, which were different from thoseof crown gall tumor tissues. On a per unit poly(A)⁺RNA basis the tumor RNA was slightly moreactive in translation than that from wounded tissues. The translationof tumor poly(A)⁺RNA was completely blocked by 0.5 mM 7-methylguanosine5'-phosphate, but not by 7-methylguanosine, suggesting the presenceof a 5'-cap structure. (Received May 15, 1982; Accepted June 30, 1982)     

Stimulation of synthesis and translational activity of polyadenylated messenger RNA in wounded potato tubers by 2, 4-dichlorophenoxyacetic acid

Mechanical wounding of potato tubers induced a rapid synthesis of RNA in the wounded tissues. Both total and polyadenylated RNA increased with time after wounding. Treatment of wounded tissues with the synthetic hormone 2,4-dichlorophenoxyacetic acid (2,4-D, 10^?4 M) further stimulated their syntheses. The poly (A) ⁺RNA from hormone treated tissues was more active in in vitro protein synthesis. The in vitro translation of poly (A) ⁺RNA from both hormone treated and untreated tissues was inhibited by 7-methylguanosin-5′ phosphate, while 7-methylguanosine had no effect, suggesting that both poly (A) ⁺RNAs contained a blocked 5′-cap structure and that the cap structure was important for in vitro protein synthesis.     

Structure and seasonal dynamics of humid tropical grasslands in Meghalaya,India

Abstract. Four humid grassland communities at three different locations in Meghalaya, India were analysed during 1988 and 1989 for species and life-form composition, diversity and dominance in relation to altitude, soil and prevailing disturbances. Due to the adverse interactive influences of exceptionally high annual rainfall (> 10 000 mm), topography and human interference on soil fertility, the grassland at Cherrapunji, at 1300 m altitude, had a low species diversity (H'= 1.74) and was dominated by three perennial grass species. Similar grasslands, at both higher and lower altitudes on fertile soil and with lower rainfall (ca. 2000 mm), showed higher diversity values (H'= 2.28 at Burnihat and 2.31 at Upper Shillong). The proportion of perennial species and chamaephytes increased with elevation. At the high altitude site a grassland under short-term protection from fires and grazing had a higher species richness, density and basal cover than an unprotected grassland. All grasslands show a clear seasonality, albeit with different patterns, with a maximum in density and basal cover in August. The differences in structure and seasonality are discussed in terms of different levels of stress.     

Isolation and characterization of salinity resistant mutant of a nitrogen-fixing cyanobacterium, Anabaena doliolum

D.V. SINGH. A.K. TRIPATHI AND H.D. KUMAR. 1991. Sodium chloride, up to 20 mmol/l concentration, had a positive effect on acetylene reducing activity and photosynthetic oxygen evolution of a paddy field cyanobacterium, Anabaena doliolum. Beyond 20 mmol/l level of salinity adverse effects appeared. A mutant resistant to 200 mmol/l NaCl was isolated by nitrosoguanidine mutagenesis. The mutant, NaCl-R₂₀₀, showed about 20–25% more nitrogenase activity and photosynthetic oxygen evolution than the parent. Better capacity of nitrogen fixation and photosynthesis possibly could help the mutant in synthesis of osmotic stabilizer to resist the salinity stress.     

Presynaptic Glutamate Receptors Regulate Noradrenaline Release from Isolated Nerve Terminals

The wide-ranging neuronal actions of excitatory amino acids, such as glutamate, are thought to be mediated mainly by postsynaptic N-methyl-D-aspartate (NMDA) and non-NMDA receptors. We now report the existence of presynaptic glutamate receptors in isolated nerve terminals (synaptosomes) prepared from hippocampus, olfactory bulb, and cerebral cortex. Activation of these receptors by NMDA or non-NMDA agonists, in a concentration-dependent manner, resulted in Ca(2+)-dependent release of noradrenaline from vesicular transmitter stores. The NMDA-stimulated release was potentiated by glycine and was blocked by Mg2+ and selective NMDA antagonists. In contrast, release stimulated by selective non-NMDA agonists was blocked by 6-cyano-7-nitroquinoxaline-2,3- dione, but not by Mg2+ or NMDA antagonists. Our data suggest that the presynaptic glutamate receptors can be classified pharmacologically as both the NMDA and non-NMDA types. These receptors, localized on nerve terminals of the locus ceruleus noradrenergic neurons, may play an important role in interactions between noradrenaline and glutamate.