Crescimento in vitro e estimulação genética de plântulas de Cattleya-91 em diferentes nutrições líquidas enriquecidas com bolhas ultrafinas oxigenadas em condição asséptica

1. A native DNA fraction was isolated from the young vegetative mycelium of Streptomyces griseus strain No. 52-1 and was compared with a similar fraction of Escherichia coli B. The endogenous RNA polymerase activities of these DNA fractions were examined. 2. Determining the base composition of the 14C labelled RNA synthesized in vitro, it was found that the conversion of 14C UTP into CMP residue of RNA is negligible in the DNA fraction of S. griseus, while it is significant in the DNA fraction of E. coli. By the proof of density gradient centrifugation, the RNA synthesized in vitro was mainly of messenger size in both species. 3. Template activity of the native DNA fractions was investigated in the presence of isolated E. coli RNA polymerase. When measuring the endogenous RNA polymerase and template activities of the DNA complexes at lower and higher ionic strength it was established that DNA complexes of E. coli under both ionic conditions behaved essentially as free DNA strands did, while endogenous and exogenous RNA polymerase activities in DNA complexes of S. griseus are inhibited in medium of lower ionic strength. Our results indicate the presence of some additional compound in the S. griseus aggregate which is absent in E. coli. This compound could function at lower ionic strength while it would be inactivated at higher ionic strength.

Size matters – The phototoxicity of TiO2 nanomaterials

Cyclic voltammetry has been used to study the effects of interactions between horse cytochrome c and solid-supported planar lipid membranes, comprised of either egg phosphatidylcholine (PC) or PC plus 20 mol.% cardiolipin (CL), on the redox potential and the electrochemical electron transfer rate between the protein and a semiconductor electrode. Experiments were performed over a wide range of cytochrome c concentrations (0-440 microM) at low (20 mM) and medium (160 mM) ionic strengths. Three types of electrochemical behavior were observed, which varied as a function of the experimental conditions. At very low cytochrome c concentration (approximately 0.1 microM), and under conditions where electrostatic forces dominated the protein-lipid membrane interaction (i.e., low ionic strength with membranes containing CL), a redox potential (approximately 265 mV) and an electrochemical electron transfer rate constant (0.09 s[-1])were obtained which compare well with those measured in other laboratories using a variety of different chemical modifications of the working electrode. Two other electrochemical signals (not reported with chemically modified electrodes) were also observed to occur at higher cytochrome c concentrations with this membrane system, as well as with two other systems (membranes containing CL under medium ionic strength conditions, and PC only at low ionic strength). These involved positive shifts of the cytochrome c redox potential (by 40 and 60 mV) and large decreases in the electron transfer rate (to 0.03 and 0.003 s[-1]). The observations can be rationalized in terms of a structural model of the cytochrome c-membrane interaction, in which association involves both electrostatic and hydrophobic forces and results in varying degrees of insertion of the protein into the hydrophobic interior of the membrane.

Surface plasmon resonance studies of complex formation between cytochrome c and bovine cytochrome c oxidase incorporated into a supported planar lipid bilayer. II. Binding of cytochrome c to oxidase-containing cardiolipin/phosphatidylcholine membranes

Phosphatidic acid and polyphosphoinositide metabolism in rod outer segments. Differential role of soluble and peripheral proteins

Association of methyl, amino and hydroxy derivatives of adenine at a mercury electrode at various sodium chloride concentrations

An efficient lighting system (Compact 3U) was successfully applied to the micropropagation of gloxinia and potato plants. To compare the in vitro growth of plantlets under Neon and Compact 3U lighting systems, gloxinia and potato shoots were cultured on suitable media at different light intensities: (1) 45 µmol m -2 s -1 (under Neon lighting system as a control); (2) 45 µmol m -2 s -1 , (3) 60 µmol m -2 s -1 , and (4) 75 µmol m -2 s -1 (under Compact 3U lighting systems). The results obtained after 3 weeks of in vitro culture and 6 weeks of acclimatization in a greenhouse showed that the growth of plantlets cultured under the Compact 3U system was better than that under Neon lighting system. The Compact 3U lighting source had a highly significant effect on the growth and development of gloxinia and potato plantlets. Besides, the data in our study also indicated that gloxinia and potato plantlets adapted differently to different lighting sources and light intensities.

An efficient lighting system (Compact 3U) was successfully applied to the micropropagation of gloxinia and potato plants. To compare the in vitro growth of plantlets under Neon and Compact 3U lighting systems, gloxinia and potato shoots were cultured on suitable media at different light intensities: (1) 45 µmol m-2s-1 (under Neon lighting system as a control); (2) 45 µmol m-2s-1, (3) 60µmol m-2s-1, and (4) 75 µmol m-2s-1 (under Compact 3U lighting systems). The results obtained after 3 weeks of in vitro culture and 6 weeks of acclimatization in a greenhouse showed that the growth of plantlets cultured under the Compact 3U system was better than that under Neon lighting system. The Compact 3U lighting source had a highly significant effect on the growth and development of gloxinia and potato plantlets. Besides, the data in our study also indicated that gloxinia and potato plantlets adapted differently to different lighting sources and light intensities.

Although the kinetic mechanism of the NADPH-cytochrome P450 oxidoreductase (P450R) reaction with cytochrome c3+ has been determined at 850 mM ionic strength [Sem, D.S., & Kasper, C. B. (1994) Biochemistry 33, 12012-12021], this mechanism is no longer valid at lower ionic strength. At 850 mM ionic strength, the mechanism is two-site ping-pong, and reaction at the electron acceptor site is itself ping-pong. As the ionic strength is decreased below 850 mM, the initial velocity profiles begin to show curvature when cytochrome c3+ is the varied substrate. These data are consistent with a mechanism that is still two-site ping-pong, but now with random sequential binding of two molecules of cytochrome c3+ at the electron acceptor site. Decreasing ionic strength also causes a change in rate-limiting steps, with (V/K)cytc and (V/K)NADPH increasing while Vmax decreases (below 500 mM ionic strength). These results are consistent with favorable ionic interactions being important for binding NADPH and cytochrome c3+ and with product (NADP+) release becoming the rate-limiting step in Vmax at low ionic strength. Vmax decreases significantly at higher ionic strength (> 500 mM), while (V/K)NADPH decreases only slightly. The DV isotope effect is largest (2.4) at 500 mM ionic strength but decreases at both low and high ionic strength as steps other than hydride transfer become more rate-limiting. D(V/K)NADPH also decreases at both low and high ionic strength, but to a lesser extent than DV.(ABSTRACT TRUNCATED AT 250 WORDS)

Early α-synuclein aggregation is overall delayed and it can occur by a stepwise mechanism

Tamm-Horsfall glycoprotein (THP) is the most abundant protein in the urine of healthy individuals, but whether it actually inhibits or promotes calcium oxalate monohydrate (COM) crystallization processes (reviewed in 1) has been the subject of a great deal of controversy. At higher pH and lower ionic strength, THP primarily inhibits COM crystal aggregation2, 3, whereas at lower pH and higher ionic strength, THP molecules are more polymerized and act as weaker inhibitors of COM crystal aggregation4. Viscosity measurements and molecular weight determinations have provided evidence that severely recurrent calcium renal stone formers excrete THPs with an abnormally high tendency to polymerize and thus with reduced inhibitory properties 4.

Immature female Sprague-Dawley rats (19-21 days old 50 gm) were used to systematically study DNA-dependent RNA polymerase activity in nuclei from the uterus after administration of 1 mcg estradiol dissolved in .1 ml of 9% NaC1 solution. Controls received only the saline solution. Experimental conditions included an excess of nucleoside 5-triphosphate and short-time assays (6 minutes) at low temperature to obtain the maximal velocity of the reaction and to minimize RNase activity. Nucleotide incorporation was measured in the absence (low ionic strength medium) or the presence (high ionic strength medium) of .25 M ammonium sulfate under various divalent cation concentrations either in the presence or absence of alpha-amanitin. The alpha-amanitin-resistant RNA polymerase activity of nuclei was identical when measured under low ionic strength conditions with either Mg or Mn and under high ionic strength in the presence of Mn (all at 4 mM concentrations). At high ionic strength alpha-amanitin-sensitive activity is about 10 times greater than activity measured at low ionic strength Mn. In all the experiments initiation of new RNA chains was negligible. Estradiol administration leads to: a 50% increase in alpha-amanitin-resistant activity within 1-2 hours under all experimental conditions; a 100% increase by 2 hours in alpha-amanitin-sensitive activity under low ionic strength conditions; but no change in alpha-amanitin-sensitive activity at 6 hours under high ionic strength conditions. Since enzyme activity measured under high ionic strength conditions mainly reflects the number of enzyme molecules engaged in transcription these results suggest that estradiol leads to an early increase in number of alpha-amanitin-resistant molecules engaged in the process of transcription while the number of alpha-amanitin-sensitive molecules remains constant. The increase in alpha-amanitin-sensitive activity obtained under low ionic strength conditions can be interpreted as either an increase in template activity or an activation of the molecules already engaged in the process of transcription or both.(AUTHORS MODIFIED)

Differential activities of putative subsarcolemmal and interfibrillar mitochondria from cardiac muscle

Comparative studies of the 17β-estradiol receptors in rabbit liver, kidney and uterus

Colloid transport with wetting fronts: Interactive effects of solution surface tension and ionic strength