Photocontrol of the hypocotyl hook opening of Sinapis alba seedlings. Involvement of phytochrome and a high irradiance response

Baumgartner, N. and Fondeville, J. C. 1989. Photocontrol of the hypocotyl hook opening of Sinapis alba seedlings. Involvement of phytochrome and a high irradiance response.
A statistical evaluation of the hypocotyl hook opening (hook opening index) was used for measurement of the hook angle in lots of etiolated Sinapis alba L. cv. Albatros seedlings. Studies of the kinetics for hook opening were carried out in continuous fluorescent white, blue and red light (6, 15 and 40 μmol m^-2s^-1) with 2-day-old dark-grown seedlings. At the beginning of the irradiation period the photoresponse in red light was the opposite to that in blue (low photon fluences). Blue rapidly induced the hook opening (in less than 20 min), while red produced hook tightening (photon fluences up to 70 mmol m^-2), which precedes the normal progressive hook opening. For low fluences, the data were consistent with the involvement of phytochrome and a specific blue light photoreceptor. A phytochrome effect was observed in the hook opening, dependent upon a high irradiance response (HIR). This HIR (like that for the inhibition of the hypocotyl elongation) was characterized by a wavelength response curve with maxima in the blue and far-red regions of the spectrum.     

Tumor Suppressor p53 Down-Regulates Tissue-Specific Expression of Tyrosinase Gene in Human Melanoma Cell Lines

Tyrosinase, the key gene in melanin pigment synthesis, is tissue-specifically expressed in melanocytic cells. Expression of this gene is regulated by various hormones, carcinogens, and environmental factors. The molecular basis underlying tyrosinase gene regulation is still not clear. In this report, we present the effects of tumor suppressor p53 protein on tyrosinase gene expression and melanin synthesis in human melanoma. After stable transfection of wild type p53 expression plasmid into a highly pigmented melanoma cell line, overexpression of wt p53 suppressed the pigmentation of the melanoma cells. The loss of pigmentation was associated with the loss of endogenous tyrosinase expression at the activity and mRNA levels. In order to determine whether the p53 repression of tyrosinase mRNA involved modulation of tyrosinase promoter activity, transient transfection approaches involving p53 expression plasmid and construct containing chloramphenicol acetyl transferase (CAT) reporter gene linked to 270 bp tissue-specific tyrosinase promoter have been used. p53 specifically repressed CAT gene expression from the tyrosinase promoter and not from the Rous sarcoma virus promoter. These data suggest that in human melanoma p53 down-regulates the tissue-specific expression of tyrosinase gene and subsequent melanin synthesis.     

Rhizobium extracellular structures in the symbiosis

The extracellular and surface polysaccharides produced by Rhizobium species constitute a composite macromolecular interface between the bacterial cell and its environment. Several of these polysaccharides are involved in the complex series of interactions leading to the establishment of an effective Rhizobium-legume symbiosis. Extracellular heteropolysaccharides (EPSs) are found in culture supernatants, while capsular polysaccharides adhere to the cell surface. Cyclic (1–2)--d glucan is a periplasmic oligosaccharide that has also been found in the culture supernatants of some strains. The lipopolysaccharides (LPSs), which form part of the outer membrane and contain the O-somatic antigens, comprise the other major group of extracellular polysaccharides. In this review we will describe the major Rhizobium extracellular structures and their role in symbiosis with leguminous plants.The authors are with the Departamento de Microbiologia y Parasitologia, Facultad de Farmacia. Universidad de Sevilla, 41012 Sevilla, Spain     

中药固真方对一些与细胞增殖有关基因表达的影响

 中药固真方对一些与细胞增殖有关基因表达的影响姚明忠,顾文聪,丁卫,韩志芬,杜国光（上海中医药大学生物化学教研室,上海２０００３２）（北京医科大学生物化学与分子生物学系,北京１０００８３）中药固真方（ＶＲＦ）具有补肾益精、延缓衰老的作用［１］．能提高成...     

Begging, food provisioning, and nestling competition in great tit broods infested with ectoparasites

Ectoparasites are a ubiquitous environmental component of breedingbirds, and it has repeatedly been shown that hematoph-agousectoparasites such as fleas and mites reduce the quality andnumber of offspring of bird hosts, thereby lowering the valueof a current brood. Selection acting on the hosts will favorphysiological and behavioral responses that will reduce theparasites' impact. However, the results of the few bird studiesthat addressed the question of whether parasitism leads to ahigher rate of food provisioning are equivocal, and the beggingresponse to infestation has rarely been quantified. A changein begging activity and parental rate of food provisioning couldbe predicted in either direction: parents could reduce theirinvestment in the brood in order to invest more in future broods,or they could increase their investment in order to compensatefor the parasites' effect on the current brood. Since the nestlingsare weakened by the ectoparasites they may beg less, but onthe other hand they may beg more in order to obtain more food.In this study we show experimentally that (1) hen fleas (Ceratophyllusgallinae) reduce the body mass and size of great tit (Parusmajor) nestlings, (2) nestlings of parasitized broods more thandouble their begging rate, (3) the male parents increase thefrequency of feeding trips by over 50%, (4) the females do notadjust feeding rate to the lowered nutritional state of nestlings,and (5) food competition among siblings of parasitized broodsis increased. Ultimately the difference in the parental feedingresponse may be understood as the result of a sex-related differencein the trade-off of i0vesting in current versus future broods.     

Characterisation of the Binding of [3H]WAY-100635, a Novel 5-Hydroxytryptamine1A Receptor Antagonist, to Rat Brain

Abstract: The specific binding of [³H]WAY-100635 {N-[2-[4-(2-[O-methyl-³H]methoxyphenyl)-1-piperazinyl]ethyl]-N-(2-pyridinyl)cyclohexane carboxamide trihydrochloride} to rat hippocampal membrane preparations was time, temperature, and tissue concentration dependent. The rates of [³H]WAY-100635 association (k₊₁ = 0.069 ± 0.015 nM^?1 min^?1) and dissociation (k_?1 = 0.023 ± 0.001 min^?1) followed monoexponential kinetics. Saturation binding isotherms of [³H]WAY-100635 exhibited a single class of recognition site with an affinity of 0.37 ± 0.051 nM and a maximal binding capacity (B_max) of 312 ± 12 fmol/mg of protein. The maximal number of binding sites labelled by [³H]WAY-100635 was ～36% higher compared with that of 8-hydroxy-2-(di-n-[³H]-propylamino)tetralin ([³H]8-OH-DPAT). The binding affinity of [³H]WAY-100635 was significantly lowered by the divalent cations CaCl₂ (2.5-fold; p < 0.02) and MnCl₂ (3.6-fold; p < 0.05), with no effect on B_max. Guanyl nucleotides failed to influence the K_D and B_max parameters of [³H]WAY-100635 binding to 5-HT_1A receptors. The pharmacological binding profile of [³H]WAY-100635 was closely correlated with that of [³H]8-OH-DPAT, which is consistent with the labelling of 5-hydroxytryptamine_1A (5-HT_1A) sites in rat hippocampus. [³H]WAY-100635 competition curves with 5-HT_1A agonists and partial agonists were best resolved into high- and low-affinity binding components, whereas antagonists were best described by a one-site binding model. In the presence of 50 µM guanosine 5′-O-(3-thiotriphosphate) (GTPγS), competition curves for the antagonists remained unaltered, whereas the agonist and partial agonist curves were shifted to the right, reflecting an influence of G protein coupling on agonist versus antagonist binding to the 5-HT_1A receptor. However, a residual (16 ± 2%) high-affinity agonist binding component was still apparent in the presence of GTPγS, indicating the existence of GTP-insensitive sites.     

Effects of nucleotide analogs on ATP hydrolysis by P-type ATPases. Comparison between the canine kidney (Na++ K+) ATPase and maize root H+-ATPase

The mechanism by which chemical energy is converted into an electrochemical gradient by P-type ATPase is not completely understood. The effects of ATP analogs on the canine kidney (Na⁺+ K⁺) ATPase were compared to effects of the same analogs on the maize (Zea mays L. cv. W7551) root H⁺-ATPase in order to identify probes for the ATP binding site of the maize root enzyme and to determine potential similarities of ATP hydrolysis mechanisms in these two enzymes. Six compounds able to modify the ATP binding site covalently were compared. These compounds could be classed into three distinct groups based on activity. The first group had little or no effect on catalytic activity of either enzyme and included 7-chloro-4-nitrobenz-2-oxa-1.3-diazole. The second group, which included azido adenine analogs. fluorescein isothiocyanate and 5′-p-fluorosulfonylbenzoyladenine, were inhibitors of ATP hydrolysis by both enzymes. However, the sensitivity of the (Na⁺+ K⁺) ATPase to inhibition was much greater than that exhibited by the maize root enzyme. The third group, which included periodate treated nucleotide derivatives and 2′,3′-o-(4-benzoylbenzoyl)adenosine triphosphate. inhibited both enzymes similarly. This initial screening of these covalent modifiers indicated that 2′,3′-o-(4-benzoylbenzoyl)adenosine triphosphate was the optimal covalent modifier of the ATP binding site of the maize root enzyme. Certain reagents were much more effective against the (Na⁺+ K⁺) ATPase than the maize root enzyme, possibly indicating differences in the ATP binding and hydrolysis pathway for these two enzymes. Two ATP analogs that are not covalent modifiers were also tested: the trinitrophenyl derivatives of adenine nucleotides were better than 5′-adenylylimidodiphosphate for use as an ATP binding probe.     

Glutamine metabolism in AS-30D hepatoma cells. Evidence for its conversion into lipids via reductive carboxylation

A study was undertaken to assess the role of a physiological concentration of glutamine in AS-30D cell metabolism. Flux of¹⁴C-glutamine to¹⁴CO₂ and of¹⁴C-acetate to glutamate was detected indicating reversible flux between glutamate and TCA cycle -ketoglutarate. These fluxes were transaminase dependent. A flux analysis was compared using data from three tracers that label -ketoglutarate carbon 5, [2-¹⁴C]glucose, [1-¹⁴C]acetate and [5-¹⁴C]glutamine. The analysis indicated that the probability of flux of TCA cycle -ketoglutarate to glutamate was, at minimum, only slightly less than the probability of flux of -ketoglutarate through -ketoglutarate dehydrogenase. The apparent Km for oxidative flux of [¹⁴C]glutamine to¹⁴CO₂, 0.07 mM, indicated that this flux was at a maximal rate at physiological, 0.75 mM, glutamine. Although oxidative flux through -ketoglutarate dehydrogenase was the major fate of glutamine, flux of glutamine to lipid via reductive carboxylation of -ketoglutarate was demonstrated by measuring incorporation of [5-¹⁴C]glutamine into¹⁴C-lipid. In media containing glucose (6 mM), and glutamine (0.75 mM) 47 per cent of the lipid synthesized from substrates in the media was derived from glutamine via reductive carboxylation and 49 per cent from glucose. These findings of nearly equal fluxes suggest that lipogenesis via reductive carboxylation may be an important role of glutamine in hepatoma cells.     

Taxonomy of Pinus species based on the seed oil fatty acid compositions

 The fatty acid compositions of the seed oils from ten pine species have been established by capillary gas-liquid chromatography of the methyl esters. With regard to either normal fatty acids or Δ5-olefinic acids, the general pattern of fatty acids did not differ from that of other pine seed oils reported previously. The main fatty acid was linoleic (9,12–18:2) acid (44.4–57.1%), followed by either oleic (9–18:1) acid (13.4–24.5%) or pinolenic (5,9,12–18:3) acid (1.5–25.2%). When applying multivariate analyses to the chemometric data (13 variables) of 49 pine species (ca. 40% of the living pine species), it was possible to distinguish between several sections: Pinea, Longifolia, Halepensis, Ponderosa-Banksiana, Sylvestris, and Cembra. The latter section was clearly divided into two sub-groups. A few species that presented a low overall content of Δ5-olefinic acids, and that grow in warm-temperate regions, were isolated from the bulk of other pine species. It is hypothesized that Δ5-olefinic acids might be related to cold-acclimation. Received: 5 June 1997 / Accepted: 17 August 1997