Alkaline pH,membrane potential,and magnesium cations are negative modulators of purine nucleotide inhibition of H+ and Cl− transport through the uncoupling protein of brown adipose tissue mitochondria

Modulators of purine nucleotide (PN) inhibition of H⁺ and Cl^– transport mediated by the uncoupling protein (UP) of brown adipose tissue (BAT) mitochondria were studied: Alkalinization strongly diminishes GDP inhibition of H⁺ transport ( log IC₅₀=–pH_out), while more intensive inhibition of Cl^– transport is only slightly altered. Higher decreases GDP inhibition of H⁺ transport. Mg²⁺, but not palmitoyl-CoA, decreases PN inhibitory ability.Simulations of conditions similar to those found in BAT cells in the resting state and in the thermogenic state showed that three factors act in concert: pH, Mg²⁺, and free fatty acids (FFA): (a) with endogenous FFA present and 2 mM ATP and 0.5 mM AMP (pH 7.1), H⁺ transport was inhibited by 95% in the absence of Mg²⁺, while by 60% with Mg²⁺; (b) 0.5 mM ATP and 1 mM AMP, H⁺ transport was inhibited by 40% without Mg²⁺ and by 30% with Mg²⁺. State b thus represents a model thermogenic state, while state a represents a resting state. However, the latter statein vivo must be accomplished either by combustion or FFA or by elimination of Mg²⁺ to attain a total inhibition of H⁺ transport (cf. a).The model of UP possessing two independent channels, an H⁺ channel and a Cl^– channel, controlled from a single PN-binding site is supported by independent kinetics by different pH dependence of H⁺ and Cl^– transport, and by a lower sensitivity of H⁺ transport to PN inhibition.     

Coenzyme Q-pool function in glycerol-3-phosphate oxidation in hamster brown adipose tissue mitochondria

We have investigated the role of the Coenzyme Q pool in glycerol-3-phosphate oxidation in hamster brown adipose tissue mitochondria. Antimycin A and myxothiazol inhibit glycerol-3-phosphate cytochromec oxidoreductase in a sigmoidal fashion, indicating that CoQ behaves as a homogeneous pool between glycerol-3-phosphate dehydrogenase and complex III. The inhibition of ubiquinol cytochromec reductase is linear at low concentrations of both inhibitors, indicating that sigmoidicity of antimycin A and myxothiazol inhibition is not a direct property of antimycin A and myxothiazol binding. Glycerol-3-phosphate cytochromec oxidoreductase is strongly stimulated by added CoQ₃, indicating that endogenous CoQ is not saturating. Application of the pool equation for nonsaturating ubiquinone allows calculation of theK _m for endogenous CoQ of glycerol-3-phosphate dehydrogenase of 3.14mM. The results of this investigations reveal that CoQ behaves as a homogeneous pool between glycerol-3-phosphate dehydrogenase and complex III in brown adipose tissue mitochondria; moreover, its concentration is far below saturation for maximal electron transfer activity in comparison with other branches of the respiratory chain connected with the CoQ pool. HPLC analysis revealed a lower amount of CoQ in brown adipose mitochondria (0.752 nmol/mg protein) in comparison with mitochondria from other tissues and the presence of both CoQ₉ and CoQ₁₀.     

Lipase-mediated esterification of racemic alcohols: A comparison of 2-substituted cyclohexanols and cyclopentanols

Summary Esterification of five- and six-membered-ring-containing alcohols catalysed by three different lipases (those from porcine pancreas, Candida cylindracea and Geotrichum candidum) was studied. Some conversions gave high stereochemical purity, but all gave low yields.     

Construction of a simple nomogram for evaluating two-wavelength spectrophotometric determination of chlorophylls

The calculation and construction of a simple nomogram to be used instead of a set of two equations in a two-wavelength spectrophotometric determination of chlorophyllsa, b, their total amount and ratio is are described. Any pair of equations can be represented nomographically by this construction.     

An observation onAlbatrellus subrubescens (Polyporaceae)

A study of the terrestrial polyporeAlbatrellus subrubescens (Murrill)Pouz. (=A. similis) was undertaken. Its morphology, taxonomy, nomenclature, distribution and ecology is discussed.     

Eine kombination von Humusstoffen mit mineral-nährstoffen und substanzen mit fungiziden eigenschaften zum bespritzen der pflanzen

Práce ově?uje mo?nost kombinace humusovýoh látek s minerálnimi ?ivinami a látkami fungicidni povahy p?i post?iku rostlin. Laboratorně byl testován fungicidní ú?inek prepará t? Herylu, Novoziru N, Sulky a Kuprikolu kombinovaných s humusovými látkami naSclerotinia fructicola (WINT.) REHM.,Alternaria brassicae (BERK.) SACC. aErysiphe graminis var.tritici MARCHAL. Ukázalo se, ?e humusové látky nesni?ují ú?innost pou?itých fungicidníoh látek. P?i testování ú?inku Novoziru N od 0,5 do 0,03 % bylo zjiětěno, ?e p?idání humusových látek dokonce zvy?uje fungicidni ú?inek preparátu a? o 12 %. P?enice pěstovaná ve skleniku ve vodní kultu?e byla uměle infikovaná.Erysiphe graminis var.tritici MARCHAL., a po dobu kultivace st?íkána týdně roztoky humusovych látek, minerá lníeh ?ivin a Novoziru N ve vzájemné kombinaci. Výsledky ukazují dvojí p?sobeni takto kombinovaných roztok?: stimula?ní p?sobení huminových kyselin s minerálním roztokem na r?st p? enice a fungicidni ú?inek na parazitni houbu. Jako nejú?inněj?í se ukázala dvojkombinace Novoziru N s humusovými látkami a Novoziru N s minerálními ?ivinami. Ve v?ech kombinacich a Novozirem N byla infekce list? potla?ena, zatímco u jiných variant byla zna?ně pokro?ilá. Ko? enový systém citlivě reagoval na post?ik list? p?enice.     

Examination of the cyst of Malamoeba locustae and of the spore of Mattesia dispora with the scanning microscope

The fine structure of the surface of cysts of the amoeba Malamoeba locustae and that of spores of the neogregarine Mattesia dispora have been examined with the scanning microscope. Freeze-drying was found to be the most convenient of the three methods tested for the preparation of the specimens. The surface of both mature and immature cysts of M. locustae is smooth, without a microrelief. By contrast, spores of M. dispora are equipped with a small, circular structure at the poles indicating the site of the future pore through which the sporozoites will emerge in the intestine of the new host. In addition, a flat relief forming small depressions is discernable on the surface of these spores at a high magnification.