Single-channel analysis of the conductance fluctuations induced in lipid bilayer membranes by complement proteins C5b-9

Summary Single-channel analysis of electrical fluctuations induced in planar bilayer membranes by the purified human complement proteins C5b6, C7, C8, and C9 have been analyzed. Reconstitution experiments with lipid bilayer membranes showed that the C5b-9 proteins formed pores only if all proteins were present at one side of the membrane. The complement pores had an average single-channel conductance of 3.1 nS at 0.15m KCl. The histogram of the complement pores suggested a substantial variation of the size of the single channel. The linear relationship between single-channel conductance at fixed ionic strength and the aqueous mobility of the ions in the bulk aqueous phase indicated that the ions move inside the complement pore in a manner similar to the way they move in the aqueous phase. The minimum diameter of the pores as judged from the conductance data is approximately 3 nm. The complement channels showed no apparent voltage control or regulation up to transmembrane potentials of 100 mV. At neutral pH the pore is three to four times more permeable for alkali ions than for chloride, which may be explained by the existence of fixed negatively charged groups in or near the pore. The significance of these observations to current molecular models of the membrane lesion formed by these cytolytic serum proteins is considered.     

Rise in plasma beta-endorphin, ACTH, and cortisol in cancer patients undergoing whole body hyperthermia

It has been previously reported that sauna-induced fevers (approximately 39 degrees C) result in rises of beta-endorphins in normal volunteers. This report describes changes in plasma beta-endorphins in cancer patients undergoing whole body hyperthermia (40.5 degrees C to 41.8 degrees C). Results presented show that there is a linear relationship between thermal stress, defined in terms of core temperature and/or duration of hyperthermia, and the quantitative rise in plasma beta-endorphin levels. Data relating to changes in ACTH and cortisol levels are in a single temperature range (41.5 degrees C--41.8 degrees C) are also reported.     

Bioenergetic Conditions of Butyrate Metabolism by a Syntrophic, Anaerobic Bacterium in Coculture with Hydrogen-Oxidizing Methanogenic and Sulfidogenic Bacteria

The butyrate-oxidizing, proton-reducing, obligately anaerobic bacterium NSF-2 was grown in batch cocultures with either the hydrogen-oxidizing bacterium Methanospirillum hungatei PM-1 or Desulfovibrio sp. strain PS-1. Metabolism of butyrate occurred in two phases. The first phase exhibited exponential growth kinetics (phase a) and had a doubling time of 10 h. This value was independent of whether NSF-2 was cultured with a methanogen or a sulfate reducer and likely represents the maximum specific growth rate of NSF-2. This exponential growth phase was followed by a second phase with a nearly constant rate of degradation (phase b) which dominated the time course of butyrate degradation. The specific activity of H₂ uptake by the hydrogen-oxidizing bacterium controlled the bioenergetic conditions of metabolism in phase b. During this phase both the Gibbs free energy (ΔG′) and the butyrate degradation rate (v) were greater for NSF-2-Desulfovibrio sp. strain PS-1 (ΔG′ = −17.0 kJ/mol; v = 0.20 mM/h) than for NSF-2-M. hungatei PM-1 (ΔG′ = −3.8 kJ/mol, v = 0.12 mM/h). The ΔG′ value remained stable and characteristic of the two hydrogen oxidizers during phase b. The stable ΔG′ resulted from the close coupling of the rates of butyrate and H₂ oxidation. The addition of 2-bromoethanesulfonate to a NSF-2-methanogen coculture resulted in the total inhibition of butyrate degradation; the inhibition was relieved when Desulfovibrio sp. strain PS-1 was added as a new H₂ sink. When the specific activity of H₂ consumption was increased by adding higher densities of the Desulfovibrio sp. to 2-bromoethanesulfonate-inhibited NSF-2-methanogen cocultures, lower H₂ pool sizes and higher rates of butyrate degradation resulted. Thus, it is the kinetic parameters of H₂ consumption, not the type of H₂ consumer per se, that establishes the thermodynamic conditions which in turn control the rate of fatty acid degradation. The bioenergetic homeostasis we observed in phase b was a result of the kinetics of the coculture members and the feedback inhibition by hydrogen which prevents butyrate degradation rates from reaching their theoretical V_max.     

Evaluation ofAphidoletes aphidimyza [Dip.: Cecidomyiidae] for control ofMyzus persicae [Hom.: Aphididae] in greenhouse and field experiments in the United States

BioControl - Greenhouse and field experiments were conducted to evaluate the potential of inoculative releases of the predatory midge,Aphidoletes aphidimyza (Rondani), on aphid populations on...     

Heavy-metal-contaminated industrial soil: Uptake assessment in native plant species from Brazilian Cerrado

Plants of the Cerrado have shown some potential for restoration and/or phytoremediation projects due to their ability to grow in and tolerate acidic soils rich in metals. The aim of this study is to evaluate the tolerance and accumulation of metals (Cd, Cu, Pb, and Zn) in five native tree species of the Brazilian Cerrado (Copaifera langsdorffii, Eugenia dysenterica, Inga laurina, Cedrela fissilis, Handroanthus impetiginosus) subjected to three experiments with contaminated soils obtained from a zinc processing industry (S₁, S₂, S₃) and control soil (S₀). The experimental design was completely randomized (factorial 5 × 4 × 3) and conducted in a greenhouse environment during a 90-day experimentation time. The plant species behavior was assessed by visual symptoms of toxicity, tolerance index (TI), translocation factor (TF), and bioaccumulation factor (BF). C. fissilis has performed as a Zn accumulator by the higher BFs obtained in the experiments, equal to 3.72, 0.88, and 0.41 for S₁, S₂, and S₃ respectively. This species had some ability of uptake control as a defense mechanism in high stress conditions with the best behavior for phytoremediation and high tolerance to contamination. With economical and technical benefits, this study may support a preliminary analysis necessary for using native tree species in environmental projects.     

Levels of Carboxyarabinitol 1-Phosphate and Related Photosynthetic Components during Leaf Development in Phaseolus vulgaris

The influence of leaf development on the levels of carboxyarabinitol1-phosphate (CA1P), carboxyarabinitol (CA), CA1P phosphataseactivity, ribulose bisphosphate carboxylase (rubisco) activity,photosynthesis, and rubisco catalytic sites was examined inPhaseolus vulgaris. Leaves were sampled at mid-day or after15 h dark over a 3 week growth period. Mid-day initial rubiscoactivities were comparable to net photosynthetic rates, reaching245 µmol (mg Chl)^-1 h^-1 at 67–100% full size (26–30µmolm^-2 s^-1). CA1P and CA were present at substantial levels inleaves of all ages (light and dark-treated, respectively), increasingby similar amounts throughout expansion. Total rubisco catalyticsites increased 2.4-fold to 58 nmol (mg Chl)^-1 during leaf growthto 66% full size, remaining constant with further expansion.CA1P phosphatase activity was particularly low in the youngestleaves, and increased 14-fold during leaf expansion. CA1P content of dark bean leaves (nmol per mg Chl) was alwaysin excess of total rubisco catalytic sites throughout development,but decreased from 2.2-fold (mol CA1P per mol sites) in theyoungest leaves to 1.4-fold at maturation. The number of rubiscocatalytic sites bound to CA1P in the dark was measured in differentaged leaves after extracting leaves with 25 mM ammonium sulfate,which stabilizes the in vivo level of CA1P bound to rubisco.These measurements demonstrated that in the youngest leavesrelatively much less CA1P was bound to rubisco catalytic sitesin the dark. This was in contrast to what occurred in dark-treatedolder leaves, in which a large proportion of catalytic siteswere bound with CA1P. We suggest that in very young bean leaveseither rubisco has a reduced affinity for CA1P, or much of theCA1P in dark leaves may be bound to another, unidentified cellularcomponent(s). (Received April 25, 1995; Accepted June 30, 1995)     

The passage of spermatozoa through the cervix of ovariectomized ewes treated with progesterone and oestrogen.

Thirty spayed ewes were used in a 2 x 3 split-plot factorial experiment (n = 5) in which oestrus was induced with 30 or 90 mug oestradiol benzoate (OB) following a period of progesterone priming. They were inseminated 36 hr after oestrogen and the numbers of spermatozoa in the caudal, mid- and cranial regions of the cervix (sub-plots) were estimated 1, 12 and 24 hr later. At each interval of time and for each region of the cervix, fewer spermatozoa were recovered from the ewes treated with 30 mug OB than from those treated with 90 mug (P less than 0-05).