拐芹根化学成分研究Ⅱ

从伞型科当归属植物拐芹(Angelica polymorpha Maxim)的根及根茎中又分得4个结晶性化合物。经物理常数测定、光谱分析,分别鉴定为欧前胡素Ⅰ,异氧化前胡内酯Ⅱ,Pabulenol Ⅲ,Phellopterin Ⅳ。     

Bacterioplankton Dynamics in the McMurdo Dry Valley Lakes, Antarctica: Production and Biomass Loss over Four Seasons

Abstract Research of the microbial ecology of McMurdo Dry Valley lakes has concentrated primarily on phototrophs; relatively little is known about the heterotrophic bacterioplankton. Bacteria represent a substantial proportion of water column biomass in these lakes, comprising 30 to 60% of total microplankton biomass. Bacterial production and cell numbers were measured 3 to 5 times, within four Antarctic seasons (October to January), in Lakes Fryxell, Hoare, and Bonney. The winter-spring transition (September to October) was included during one year. Lake Fryxell was the most productive, but variable, lake, followed by Lakes Bonney and Hoare. Bacterial production ranged from 0 to 0.009 μg C ml-1 d-1; bacterial populations ranged from 3.2 x 10(4) to 4.4 x 10(7) cells ml-1. Bacterial production was always greatest just below the ice cover at the beginning of the season. A second maximum developed just above the chemocline of all the lakes, as the season progressed. Total bacterioplankton biomass in the lakes decreased as much as 88% between successive sampling dates in the summer, as evidenced by areal integration of bacterial populations; the largest decreases in biomass typically occurred in mid-December. A forward difference model of bacterial loss in the trophogenic zone and the entire water column of these lakes showed that loss rates in the summer reached 6.3 x 10(14) cells m-2 d-1 and 4.16 x 10(12) cells m-2 d-1, respectively. These results imply that bacteria may be a source of carbon to higher trophic levels in these lakes, through grazing.     

Virulence of Yersinia enterocolitica is closely associated with siderophore production, expression of an iron-repressible outer membrane polypeptide of 65 000 Da and pesticin sensitivity

Iron-repressible outer membrane proteins (Irp) and siderophore production of Yersinia enterocolitica, serotype 08, were subjected to analysis. Here four Irps of apparent molecular weights of 62000, 65000, 74000 and 75000 could be identified which were expressed constitutively by a fur mutant. Production of a novel catechol-containing siderophore (denoted yersiniabactin) was detected by siderophore-indicator agar (chrome azurol S) and feeding experiments. Growth support by yersiniabactin under iron-restricted conditions was TonB- and Irp65-dependent and correlated with pesticin-sensitivity of Yersinia enterocolitica and Escherichia coliø. From these results we conclude that Irp65 of Y. enterocolitica functions as yersiniabactin receptor (FyuA) and as pesticin receptor. By immunoblotting using rabbit antibodies against Irp65 and chrome azurol S-agar, we were able to demonstrate that all tested mouse-lethai Y. enterocoiitica and Yersinia pseudotuberculosis strains of different serotypes express siderophores and Irp65. Moreover, the anti-lrp65 rabbit serum did not cross-react with the known iron-repressible high-molecular-weight proteins (HMWPs). Evidently, the mouse lethality trait in enteropathogenic Yersinia spp. is closely associated with a novel iron-uptake system, comprising the production of a siderophore and a siderophore receptor of apparent molecular mass 65 000 Da.     

Complex binding interactions between multicomponent mixtures and odorant receptors in the olfactory organ of the Caribbean spiny lobster Panulirus argus

Our study was designed to examine how components of complex mixtures can inhibit the binding of other components to receptor sites in the olfactory system of the spiny lobster Panulirus argus. Biochemical binding assays were used to study how two- to six-component mixtures inhibit binding of the radiolabeled odorants taurine, L-glutamate and adenosine-5'-monophosphate to a tissue fraction rich in dendritic membrane of olfactory receptor neurons. Our results indicate that binding inhibition by mixtures can be large and is dependent on the nature of the odorant ligand and on the concentration and composition of the mixture. The binding inhibition by mixtures of structurally related components was generally predicted using a competitive binding model and binding inhibition data for the individual components. This was not the case for binding inhibition by most mixtures of structurally unrelated odorants. The binding inhibition for these mixtures was generally smaller than that for one or more of their components, indicating that complex binding interactions between components can reduce their ability to inhibit binding. The magnitude of binding inhibition was influenced more by the mixture's precise composition than by the number of components in it, since mixtures with few components were sometimes more inhibitory than mixtures with more components. These findings raise the possibility that complex binding interactions between components of a mixture and their receptors may shape the output of olfactory receptor neurons to complex mixtures.      

Evaluating the forced oscillation technique in the detection of early smoking-induced respiratory changes

Background  

Early detection of the effects of smoking is of the utmost importance in the prevention of chronic obstructive pulmonary disease (COPD). The forced oscillation technique (FOT) is easy to perform since it requires only tidal breathing and offers a detailed approach to investigate the mechanical properties of the respiratory system. The FOT was recently suggested as an attractive alternative for diagnosing initial obstruction in COPD, which may be helpful in detecting COPD in its initial phases. Thus, the purpose of this study was twofold: (1) to evaluate the ability of FOT to detect early smoking-induced respiratory alterations; and (2) to compare the sensitivity of FOT with spirometry in a sample of low tobacco-dose subjects.     

Noncontact dipole effects on channel permeation. III. Anomalous proton conductance effects in gramicidin

Proton transport on water wires, of interest for many problems in membrane biology, is analyzed in side-chain analogs of gramicidin A channels. In symmetrical 0.1 N HCl solutions, fluorination of channel Trp(11), Trp-(13), or Trp(15) side chains is found to inhibit proton transport, and replacement of one or more Trps with Phe enhances proton transport, the opposite of the effects on K(+) transport in lecithin bilayers. The current-voltage relations are superlinear, indicating that some membrane field-dependent process is rate limiting. The interfacial dipole effects are usually assumed to affect the rate of cation translocation across the channel. For proton conductance, however, water reorientation after proton translocation is anticipated to be rate limiting. We propose that the findings reported here are most readily interpreted as the result of dipole-dipole interactions between channel waters and polar side chains or lipid headgroups. In particular, if reorientation of the water column begins with the water nearest the channel exit, this hypothesis explains the negative impact of fluorination and the positive impact of headgroup dipole on proton conductance.     

Establishment and maintenance of stable spatial patterns in lacZ fusion transformants of Polysphondylium pallidum.

Polysphondylium pallidum cells were transformed with a construct containing the Dictyostelium discoideum ecmA promoter fused to a lacZ reporter gene. Two stably transformed lines, one in which beta-galactosidase (beta-gal) is expressed in apical cells of the fruiting body (p63/2.1), and one in which it is expressed in basal cells (p63/D), have enabled us to infer how cells move during aggregation and culmination. Several types of cell movement proposed to occur during slime mold culmination, such as random cell mixing and global cell circulation, can be ruled out on the basis of our observations. Cells of the two transformant lines express beta-gal very early in development. In both cases, stained cells are randomly scattered in a starving population. By mid to late aggregation, characteristic spatial patterns emerge. Marked cells of p63/2.1 are found predominantly at tips of tight aggregates; those of p63/D accumulate at the periphery. These patterns are conserved throughout culmination, showing that marked cells maintain their relative positions within the multicellular mass following aggregation. Neither the apical nor the basal pattern appears to be regulated within the primary sorogen by de novo gene expression or by cell sorting as whorls are formed. However, marked cells within a whorl re-establish the original pattern in secondary sorogens. This must be achieved by cell migration, since beta-gal is not re-expressed.     

Analysis of developmentally expressed antigens in Polysphondylium pallidum

A series of monoclonal antibodies were previously raised against developing Polysphondylium pallidum cells. In this work, six of these antibodies have been used as probes to identify and characterize antigens regulated during development. Soluble and membrane fractions of P. pallidum cells at six stages of development or three stages of cyclic adenosine monophosphate (cAMP)-induced development were run in sodium dodecyl sulfate (SDS)-polyacrylamide gels and subjected to Western blot analysis. Three of the monoclonals, anti-Tp200, anti-Tp423, and anti-Pg101, stain sorogen tips. Tp423 and Tp200 are membrane-associated antigens; both are stable to urea extraction, and Tp200 remains in the membrane after NaOH extraction. Tp423 is present in starved cells but is more prominent in sorogens and particularly in cAMP-developed cells. In contrast, Tp200 is first detected in early to mid-aggregation and is more abundant late in development. Pg101, which is expressed as a gradient with its highest concentration in tips, first appears in tight aggregates but is much more abundant in sorogens; unlike the Tp antigens, Pg101 is not greatly induced in cAMP-developed cells. All three of these antigens undergo changes in apparent molecular weight at the tight aggregate or sorogen stage: The gel mobilities of Tp200 and Pg101 increase, whereas that of Tp423 decreases. In addition to the tip-specific monoclonals, two monoclonals that stain all but the tips of sorogens have been used for analysis. One of these, anti-3D10Pnk stains most cells within secondary tips, whereas anti-3D10Dif does not. 3D10Dif is membrane associated; it is present very early in development, increasing two- to threefold through the sorogen stage and diminishing in late cAMP-developed cells. 3D10Pnk is a mostly soluble species first detected in late streaming. Anti-1c3, a sixth monoclonal, which stains nuclei uniformly throughout sorogens, is also developmentally expressed. 1c3 is mainly membrane associated and is expressed from late streaming through the sorogen stage.