The redox state of pyridine nucleotides controls permeability of uncoupled mitochondria to K+

Heart mitochondria respiring in the presence of P_i release endogenous K⁺ to a sucrose medium when an uncoupler is added. The uncoupled mitochondria retain K⁺, however, if the oxidation of NAD(P)H is prevented by the addition of rotenone or antimycin. Addition of rotenone, once the uncoupler-dependent K⁺-efflux has been initiated, results in a rapid reduction of NAD(P) and a simultaneous decrease in permeability to K⁺. These changes are independent of respiration. The results suggest that a latent pathway for K⁺-permeability is present in the membrane, that it can be opened and closed reversibly, and that it reflects, either directly or indirectly, the redox status of mitochondrial pyridine nucleotides. The possible relationship of this putative pathway to those available for Ca²⁺ uptake and release is considered.     

Methods in clinical hemorheology: the continuous measurement of arterial blood density and blood sound speed in man

Both blood density and sound speed are closely related to total protein concentration in blood and, as a consequence, to rheologically important parameters of blood. Two methods that permit continuous measurement of these properties, the mechanical oscillator technique and the new ultrasonic technique, were used for measuring blood protein concentration over a continuous period of time in a group of hemodialysis patients and in volunteers. It was seen that the concentration of the components of blood varies considerably. This variability is related to transport phenomena within as well as to the flow of masses across the cardiovascular compartment. From the continuous measurement of concentrations during hemodialysis treatment, relative changes in blood volume can be recorded in order to control the fluid balance of the patient. Rapid fluctuations at the macroscopic scale with periods of 5 to 30 seconds are due to heterogeneities at the microscopic scale and to the particular rheological behaviour of the red blood cells at the level of the capillaries and the small blood vessels. The amplitude of rapid oscillations increased up to 1.2% in terms of hematocrit values when there was rhythmic, spontaneous breathing at various frequencies. The measurement of concentrations at an accessible measuring site may be used to investigate the rheology of blood in the human microvasculature.     

Wood preservation hygiene and environment in the lime-light of actually

Summary Under the ?Bois plus? scheme, the CTBA is currently developing a third party certification, based on the Scrivener law, with the aim of defending the consumers' interests. At this early stage, wood preservatives and treated wood are checked for the efficacy of treatments in order to ensure the stability and security of works in buildings and civil engineering. According to the different classes of risks in service, ?Bois plus? provides the most adeguate level of protection. In the close future, the industry is planning to incorporate, with the help of the CTBA and experts, health criteria within the frame of the ?Bois plus? certification scheme. The means could beSafety indexes, which are objectives of quality for professionals.Safety indexes are concentrations of substances in wood which can be taken as safe for humans and the general environment, while still toxic for the wood pests. This attractive experience aims to make with the brandname ?Bois plus? a synonym of efficacy and safety. This approach meets the essential requirements 1, 3, 4 of the 89/106 EEC directive: mechanical resistance and stability/hygiene, health and environment/safety in use.     

The stimulation of 2-deoxy-D-glucose transport in control and virus-transformed cells by ethidium bromide

Recently we demonstrated that ethidium bromide altered the plasma and subcellular membrane glycoproteins in control and virus transformed cells. It is reported here that ethidium bromide also stimulated the membrane associated process of sugar transport. The K_m of the virus transformed cells and the ethidium bromide treated cells is the same as that of the control cells while the maximum velocity as compared to the control cells is significantly increased. The transport of 2-deoxy-D-glucose was inhibited by glucose, cytochalasin B and neuraminidase but was unaffected by variations in cell density or pH of the incubation medium.     

Potential Toxicological Problems Associated with Antioxidants in Plastics and Rubber Consumables

Antioxidants and stabilisers are of critical importance in the manufacture and use of polymer artifacts. Most conventional additives are readily leached from plastics or rubbers by foodstuffs or body fluids with consequent danger associated with the potential toxicity in the body. Strategy for the development of biologically “safe” stabilisation systems for polymers are discussed and it is concluded that the attachment of the appropriate reactive functional group to the polymer backbone by “reactive processing” provides the best means of immobilising the functional group to leaching fluids without sacrificing its protective action.     

Book Review

International Journal of Primatology -     

The trajectory of a stiff rod in a curved potential energy trough

The equilibrium trajectory of the axis of a rod subject to an externally imposed curved potential energy trough tends to conform to the shape of the curved trough, but also tends to be straight because of elastic resistance to bending. The actual path of the axis is a balance between the two extremes. We consider a potential energy trough centered along a circular arc of radiusR. For a rod of small length compared toR, we show that the axis at equilibrium forms an arc of a circle of radius greater thanR. The value of the radius of the axial path depends on the relative values of the Hooke’s Law bending constant for the rod and the depth and width of the trough. Motivation for the calculation is provided by nucleosomal DNA, which conforms to the surface of a roughtly cylindrical histone core at physiological ionic strength, but is observed to unwind into a partially extended conformation at very low ionic strength. We suggest that the rigidity to bending of short DNA segments becomes sufficiently great at low ionic strength to overcome attractive interactions with the histone surface. Alternately, of course, if during the cell cycle mutually attractive forces between DNA and histone core are weakened at constant ionic strength, the same type of unfolding would be expected to occur as the strength of the DNA-histone contacts drops below the level required to overcome elastic resistance to bending of the DNA rod.     

Theoretical significance of the condition δ=2μ in bacterial chemotaxis

First-order spatial gradients are reliquished in the Schrödinger-Bloch equation for bacterial chemotaxis if and only if the flux coefficient-motility ratio equals 2, the precise value measured in recent experiments onEscherichia coli attracted by oxygen. Moreover, for δ/μ=2 the Schrödinger-Bloch function Ψ is simply equal to the number of bacteria cells per unit volume divided by the chemoattractant concentration.     

In Vitro Studies of α-Carboxyl-3-Thienylmethyl Penicillin,a New Semisynthetic Penicillin

The activity of a new semisynthetic penicillin, α-carboxyl-3-thienylmethyl penicillin (BRL-2288) was determined against 535 clinical isolates of gram-negative bacilli, by using the tube dilution technique. Nearly 80% of isolates of Proteus spp. were inhibited by 3.12 μg or less of this antibiotic per ml. BRL-2288 was as active as ampicillin against Escherichia coli. It was slightly more active than carbenicillin or 6-(d-α-sulfoaminophenylacetamido)-penicillanic acid against Pseudomonas sp., with over half of the isolates being inhibited by 50 μg or less of BRL-2288 per ml. Isolates of Klebsiella sp. were routinely resistant to this antibiotic. The drug was bactericidal against most sensitive organisms. BRL-2288 was less active against large inocula. A strain of Pseudomonas sp. which developed resistance to carbenicillin also developed resistance to BRL-2288 simultaneously.